UK Hoverflies (Syrphidae)'s Journal

February 08, 2024

What to look out for: October to February

The 'off season' for hoverflies really begins toward the end of October and continues into early March. (see the end for a list of species still above 10%opa in October). Using data from NBN atlas and excluding those marked 'larva', only 2% of all hoverfly records occur in the months Nov-Feb. Nevertheless, that is some. I do not believe any species achieve 10%opa from November to January, the only species to do so in February is Melangyna quadrimaculata - see March's article for information about that.

Some 46 species have records from January (I excluded larvae from the search but I can't guarantee that none of the results are 'undeclared larvae!'). It must be said though that you are considerably more likely to see adult hoverflies in the winter in the south.

The most likely species to see are Eristalis tenax, Eristalis pertinax, Eristalinus aeneus (near the coast), Episyrphus balteatus, Meliscaeva auricollis, and Melanostoma species. These may actually overwinter as adults. I have personally seen Eristalis tenax and Episyrphus balteatus on New Year's Day before!

It is worth therefore looking for hoverflies basking in sunlight on mild winter days. It may be possible to attract them by spraying foliage with a solution of sugar in water. In late winter, catkins (especially Salix) and early flowering Prunus species may be useful hunting grounds.

Another way to see hoverflies in winter is by looking for their larvae...

Larvae can most easily be found by searching through leaf litter. In the winter most larvae will be in a state of diapause (a sort of hibernation, if you will). Diapause often involves a change from bright to dull colours (green larvae often go brown). There is a separate project specifically for UK hoverfly larvae that also feeds into the HRS. Rotheray's guide to larvae is still very useful and can be found here. Many larvae can be identified to genus, and some even to species.

The following species remain over 10%opa in October
Didea fasciata 14%opa
Eristalis abusiva 12%opa, E. pertinax 20%opa, E. tenax 34%opa
Eupeodes luniger 22%opa
Helophilus pendulus 17%opa
Melanostoma scalare 11%opa
Neoascia podagrica 21%opa
Platycheirus albimanus 21%opa, P. manicatus 10%opa, P. scutatus 11%opa
Sericomyia silentis 16%opa, S. superbiens 15%opa
Syrphus ribesii 14%opa, Syrphus torvus 22%opa
Xanthandrus comtus 13%opa

Posted on February 08, 2024 10:06 AM by matthewvosper matthewvosper | 0 comments | Leave a comment

What to look out for: September

[For explanations and definitions see here. Almost all of the data here is derived from NBN Atlas and the species information from Steven Falk's Flickr and the HRS website]

Things really wind down in September. Only three species peak in this month, although plenty of summer species will hang around for a while - in fact a further 94 species remain above 10%opa in September, and they are listed at the end.

September is the best month to see....

*TOP TARGET*


Callicera spinolae (73,-80%)

A rare treat. Females can be easily distinguished from the similar C. aurata by their all-orange femora. Both sexes have dull black hind margins to the tergites, and relatively conspicuous bands of pale hairs on the tergite hind margins.

This hoverfly appears from nowhere in September and can be seen into October, often on Ivy. Larvae live in tree rot holes. It has expanded out of its previous stomping ground in East Anglia and now occupies an area east of a line from Brighton to Rutland. Falk's pics

Didea fasciata (34,-45%)

This species has been building for a long time (it first surpassed 10%opa in April!) but it peaks now. It can be seen on a wide range of flowers, including ivy. A view of the pale halteres is crucial. Falk's pics

Other species that peak in September [species in square brackets usually require microscopy to identify]:

Helophilus pendulus (0,-24%)

The following species remain above 10%opa in September

- those still over 50%opa highlighted in bold.


Pipizinae Heringia vitripennis 25%opa
Pipiza lugubris 17%opa
Triglyphus primus 11%opa
Eristalinae Callicera aurata 14%opa
Cheilosia bergenstammi 24%opa, C. caerulescens 20%opa, C. cynocephala 19%opa, C. griseiventris 10%opa, C. impressa 26%opa, C. latifrons 34%opa, C. longula 18%opa, C. mutabilis 17%opa, C. pagana 16%opa, C. scutellata 34%opa, C. soror 51%opa, C. vernalis 33%opa, C. velutina 13%opa
Eristalinus aeneus 17%opa
Eristalis abusiva 65%opa, E. arbustorum 52%opa, E. cryptarum 38%opa, E. horticola 40%opa, E. intricaria 16%opa, E. nemorum 32%opa, E. pertinax 57%opa, E. rupium 18%opa, E. tenax 73%opa
Eumerus funeralis 25%opa, E. strigatus 17%opa
Ferdinandea cuprea 42%opa, F. ruficornis 27%opa
Helophilus hybridus 52%opa, H. trivittatus 32%opa
Lejogaster metallina 13%opa
Lejops vittatus 22%opa
Myathropa florea 34%opa
Neoascia geniculata 14%opa, N. interrupta 11%opa, N. podagrica 51%opa
Rhingia rostrata 57%opa
Riponnensia splendens 21%opa
Sericomyia silentis 60%opa, S. superbiens 95%opa
Sphegina clunipes 10%opa
Syritta pipiens 32%opa
Volucella inanis 17%opa, V. zonaria 33%opa
Xylota florum 12%opa, X. segnis 23%opa, X. sylvarum 16%opa
Syrphinae Baccha elongata 25%opa
Chrysotoxum arcuatum 33%opa
Dasysyrphus albostriatus 33%opa, D. tricinctus 27%opa
Didea alneti 25%opa
Epistrophe grossulariae 34%opa
Episyrphus balteatus 27%opa
Eriozona syrphoides 14%opa
Eupeodes bucculatus 50%opa, E. corollae 11%opa, E. latifasciatus 49%opa, E. luniger 71%opa, E. nielseni 13%opa, E. nitens 21%opa
Leucozona glaucia 33%opa
Megasyrphus erraticus 22%opa
Melangyna arctica 11%opa, M. barbifrons 13%opa, M. compositarum 14%opa, M. labiatarum 15%opa, M. umbellatarum 22%opa
Melanostoma mellinum 31%opa, M. scalare 41%opa
Meliscaeva cinctella 36%opa
Parasyrphus lineola 18%opa
Platycheirus albimanus 62%opa, P. clypeatus 15%opa, P. europaeus 11%opa, P. manicatus 14%opa, P. peltatus 38%opa, P. scutatus 52%opa, P. sticticus 10%opa
Pyrophaena granditarsus 38%opa
Scaeva selenitica 25%opa, S. pyrastri 12%opa
Sphaerophoria batava 10%opa, S. loewi 25%opa, S. rueppellii 11%opa, S. scripta 24%opa, S. virgata 14%opa
Syrphus ribesii 71%opa, S. torvus 54%opa, S. vitripennis 60%opa
Xanthandrus comtus 25%opa
Xanthogramma pedissequum 11%opa

Posted on February 08, 2024 10:02 AM by matthewvosper matthewvosper | 0 comments | Leave a comment

What to look out for: August

[For explanations and definitions see here. Almost all of the data here is derived from NBN Atlas and the species information from Steven Falk's Flickr and the HRS website]

This is the last of the big months for hoverflies. Many species that peaked in previous months are still busily buzzing around, but the number of species at peak this month is a fair bit lower, at 41. The number reaching 10%opa for the first time is a big fat 0 (although there is one species waiting for September - I'll keep you in suspense!).

August is the best month to see....

...Cheilosia soror (45,-44%)

One of the three Cheilosia with fungus-feeding larvae - subgenus Eucartosyrphus - and the only one with orange antennae. Females of the subgenus are easily identified by the pale tip to the scutellum, so female soror is easy to determine by the combination 'pale-tipped scurellum + orange antennae'. Males are more challenging to identify. Be sure to get the best possible pictures of the eyes (not hairy), bristles on the scutum, the leg and antennae colour. Hairs under the hind femur also help with males.

This is the only Cheilosia that remains above 50%opa in September, and it can be seen on hogweed and later, ivy. Common as far north in England as the Wash, although uncommon in the south west peninsula and Wales. Scattered records as far north as Newcastle. Larvae have apparently been bred from truffles, but other fungi may well be used. Falk's pics

*TOP TARGET*


...Meligramma guttata (76,-100%)

This rare Meligramma has more the appearance of a Melangyna. It is most easily identified from females which have yellow stripes along the side of the scutum (like Sphaerophoria), and two yellow dust spots (often merged into one large spot) on the back of the scutum, in front of the scutellum. Males are harder to identify, but both sexes have particularly small markings on T2, and very little yellow on the hind margins of T4 and 5. The markings are more 'bar-shaped' than triangular, unlike Meligramma trianguliferum.

The species is widespread across Great Britain, but there are hotspots between Nottingham and the Yorkshire Dales, around County Durham and Tyneside, and the central belt of Scotland. Falk's pics

*TOP TARGET*


...Neoascia podagrica (7,-98%)

One of three Neoascia with clouded crosveins in the wing. It can be tentatively distinguished from the other two by not having oblique markings on T2, and not having markings on T4. But the best way to make sure is a clear picture of the underside of the thorax, showing the area in front of the hind coxae: no mean feat in such a small fly.

It is ubiquitous everywhere. The larvae live in wet manure and compost, or around the edge of ponds. The adults can be found with a sweeping net, but they do regularly visit low-growing flowers. Falk's pics

*TOP TARGET*


...Platycheirus peltatus (22,-96%)

As usual with Platycheirus the male front leg is key. Males in the peltatus-group of species are notable for their large paddle-shaped forebasitarsi. peltatus itself is larger than the other two, (amplus and neilseni) with larger markings on T2 A front view of the shape and hair tufts of the*middle* tibia is also valuable in distinguishing these.

Ubiquitous everywhere in Great Britain. Damp grassy areas and hedgrows.

...Sericomyia superbiens (27,-68%)

A hairy bumble-bee mimic, most similar to Mallota cimbiciformis - but the radial wing vein is straight. It is also similar to the oxycanthae form of the Spring-flying Matsumyia berberina, but the wings have a cloud.

Occurs north and west of a straight line from Weymouth to Scarborough, with an outpost in Norfolk. Visits flowers. Larvae are unknown, but probably develop in wet mud.

Also look out for Didea fasciata this month, which is very close to its peak - be sure to get a shot of the pale halteres!

The following species were discussed in July's 'First month you may find', but they peak now:

Triglyphus primus (59,-100%)

The following species were discussed in June's 'First month you may find', but they peak now:

Eristalis rupium (38,-71%)

The following species were discussed in May's 'First month you may find', but they peak now:

Cheilosia impressa (25,-81%)

Other species that peak in August [species in square brackets usually require microscopy to identify]:

Callicera aurata (67,-40%)
[C. carbonaria (79,-100%), C. cynocephala (71,-100%), C. latifrons (43,-100%), C. mutabilis (63,-100%), C. vulpina (47,-93%)
Dasysyrphus albostriatus (20,+53%), D. tricinctus (24,-45%)
Episyrphus balteatus (0,+45%)
Eriozona syrphoides (40,-64%)
Eristalis arbustorum (3,-41%), E. pertinax (1,+57%), E. tenax (1,+91%)
[Eumerus funeralis (34,-96%), E. strigatus (30,-99%)]
Eupeodes latifasciatus (19,-55%), E. luniger (8,0%)
Ferdinandea ruficornis (65,-100%)
Helophilus hybridus (16,-63%), H. trivittatus (17,-18%)
Leucozona glaucia (11,-33%)
Melangyna umbellatarum (35,-61%)
Meliscaeva cinctella (12,-49%)
Myathropa florea (4,+174%)
Paragus albifrons (85,-100%)
Pelecocera caledonica (92,-100%)
Rhingia rostrata (32,+32%)
Scaeva albomaculata (100,-100%), S. selenitica (37,-9%)
Sericomyia silentis (3,-48%)
[Syrphus vitripennis (6,-99%)]
Volucella inanis (18,+309%), V. zonaria (16,+1034%)


Posted on February 08, 2024 09:53 AM by matthewvosper matthewvosper | 0 comments | Leave a comment

What to look out for: July

[For explanations and definitions see here. Almost all of the data here is derived from NBN Atlas and the species information from Steven Falk's Flickr and the HRS website]

Another big month for hoverflies. For the first time in the year, more species are past their peak than not - but many of those species are still around in good numbers. 71 species peak this month, but only 3 reach 10%opa for the first time. The 84 species that peaked last month are still around, of course!

July is the best month to see....

...Anasimyia lunulata (46,-98%)

This Anasimyia is very similar to A interpuncta, a clear view of the markings on T3-4 (especially at the sides), and a side view of the face profile will help to separate them. Its distribution has apparently been decreasing, and records from the last ten years are restricted to Devon/Cornwall and Wales, especially the north west and Anglesey. There are early 21st century records from around Godalming and Norfolk. It is a species of bogland, perhaps associated with sphagnum mosses and bog-bean. Falk's pics

*TOP TARGET*


...Cheilosia proxima (21,-97%)

In general with Cheilosia it really is a case of 'the more angles the better'! With proxima the underside of the abdomen should be heavily dusted, it is also useful to capture the bristles on the scutellum, the side profile of the face and the colours of the legs - but that view of the underside of the abdomen is particularly valuable.

The larvae are known to develop in the rosettes of marsh thistle, but Falk states that it is likely they also develop in other thistles, since this is also a common species in dry grassland where marsh thistle is not present. Falk's pics. A ubiquitous species, only becoming somewhat rarer north of Dundee.

*TOP TARGET*


...Pyrophaena granditarsus (7,-93%) and P. rosarum (15,-90%)

Very distinctively marked species - still regarded as Platycheirus by many. Male P. granditarsus have remarkable hooked modifications of both the front and middle tarsi. These species are ubiquitous in distribution. They are found in wet grassland and often hover around tall vegetation such as rushes and reeds, and it may be productive to look for them on the stems. They visit a wide range of flowers.

...Paragus haemorrhous (18,-97%) and Paragus tibialis (70,-100%)

So it's a bit ambitious to put these here, but given how common P. haemorrhous is, I think it's worth it. These are tiny flies: only males are really distinguishable. Firstly though, especially if you are near the Thames estuary/North sea coast of Kent, it is worth getting a very good picture of the eyes - vertical bands of hair in the eyes indicate the critically endangered P albifrons. If there are no bands of eye hairs, males can be distinguished from the underside of the abdomen, by the size of the genitals, and the shape of the pregenital sternites. (Although tibialis should only be encountered in the south from Lyme Regis to London, it has been recorded in western Wales.)

The following species were discussed in June's 'First month you may find', but they peak now:

Cheilosia scutellata (36,-77%), Chrysogaster cemiteriorum (29,-90%), Lejops vittatus (67,-100%)

The following species were discussed in May's 'First month you may find', but they peak now:

Chrysotoxum elegans (51,-97%), Eupeodes bucculatus (63,-100%), Eupeodes nitens (69,-100%), Lejogaster tarsata (36,-97%), Parhelophilus consimilis (55,-100%), Parhelophilus versicolor (33,-100%)

The following species were discussed in April's 'First month you may find', but they peak now:

Neoascia interrupta (56,-96%)

The following species were discussed in March's 'First month you may find', but they peak now:

Eristalinus aeneus (30,-51%), Syrphus torvus (13,-68%)

Other species that peak in July [species in square brackets usually require microscopy to identify]:

Blera fallax (77,-100%)
Cheilosia illustrata (7,-29%), [C ahenea (95,-100%), C. longula (50,-100%), C. velutina (76,-100%), C. vernalis (21,-100%)]
Chrysogaster solstitialis (12,-52%)
Chrysotoxum bicinctum (10,-31%), C. festivum (27,+63%), C. verralli (46,+23%)
Didea alneti (87,-100%)
Epistrophe grossulariae (13,-8%)
Eristalinus sepulchralis (14,-67%)
Eristalis horticola (10,-56%), E. intricaria (6,-43%), E. nemorum (9,-24%)
Eupeodes corollae (6,+39%)
Helophilus groenlandicus (100,-100%)
Heringia senilis (92,-100%)
Leucozona laternaria (25,-56%)
Megasyrphus erraticus (58,-88%)
Melangyna sexguttata (=compositarum) (49,-94%)
Melanogaster aerosa (58,-100%)
Melanostoma mellinum (3,-88%)
[Myolepta dubia (71,-74%), M. potens (92,-100%)]
[Neoascia geniculata (39,-98%), N. tenur (5,-99%)]
Parasyrphus lineola (57,-73%)
Pelecocera tricincta (66,-55%)
Pipiza lugubris (68,-93%)
Pipizella maculipennis (90,-100%)
Platycheirus albimanus (1,-71%), P. aurolateralis (88,-100%), P. clypeatus (8,-99%), P. nielseni (37,-100%), P. occultus (29,-99%)
Scaeva pyrastri (7,+18%)
Sphaerophoria loewi (85,-100%), S. rueppellii (44,-64%), S. scripta (5,+25%), [S. fatarum (58,-96%), S. interrupta (14,-98%), S taeniata (65,-100%)]
Syritta pipiens (2,-37%)
Syrphus ribesii (3,-38%)
Volucella pellucens (4,+78%)
Xanthandrus comtus (41,-69%)
Xanthogramma stackelbergi (71,-15%)
Xylota florum (48,-95%), X. sylvarum (17,-41%), X. tarda (68,-100%)

July may be the first month you see...

*TOP TARGET*


...Triglyphus primus (59,-100%)

46%opa in July. A Pipizine notable because the abdomen is dominanted by T2+3, with T4 hardly visible. A view of the face will help clarify that it is a Pipizine, not a Cheilosia. The upper-outer cross vein meets the marginal at an acute angle, like in Pipiza, Heringia and Neocnemodon. The legs are partly pale, and not thickened.

This small species is associated with waste ground and urban brownfield sites as well as other thermophyllic environments like dry meadows and heathland. The larvae appear to be specific predators of the Mugwort Gall Aphid (Cryptosiphum artemisiae) that forms galls on Common Mugwort (Artemisia vulgaris). So look out for this plant! T. primus occurs in England south of York and through the Midlands, becoming rarer south west of a line from Worcester to Brighton.

Other species exceeding 10% of peak abundance (%opa) for the first time in July are [species in square brackets usually require microscopy to identify]:

Sericomyia superbiens (27,-68%) 19%opa
Volucella inanis (18,+309%) 52%opa


Posted on February 08, 2024 07:30 AM by matthewvosper matthewvosper | 0 comments | Leave a comment

What to look out for: June

[For explanations and definitions see here. Almost all of the data here is derived from NBN Atlas and the species information from Steven Falk's Flickr and the HRS website]

More species peak in June than any other month (81), but only 30 are exceeding 10% of peak abundance for the first time. It's a good time for flower feeders. Remember, hoverflies like open flowers with easily accessible nectar. Umbellifers (esp. Apiaceae) and asters are particularly popular: small flat flowers in preference to deep tubular or bell-shaped ones. Having said that - don't forget to keep an eye on low vegetation, tree trunks etc.

June is the best month to see....

...Didea intermedia (65,-83%)

Didea species are distinctive due to the dipped radial vein and the rather angry-looking abdomen markings - strongly angled spots on T2. D intermedia is distinguished from the other common species fasciata by the black haltere knob - so do your best to get a clear view of the side under the wing. The rare D alneti usually has broken bands on T3-4 with a greenish colour, and no markings on T5 (the others have a complete bands on T3-4 and little markings in the front corners of T5). D intermedia and alneti have face stripes (alneti less so) which fasciata usually lacks. The female frons of Didea sports a bold black inverted Y marking: this falls short of the lunule in intermedia but usually reaches the lunule in the others. The scutellum of intermedia is a slightly characteristic pale colour with a dark rim.

This species' larvae are associated with pine aphids, and it is rarely found far from conifers. Its distribution is blotchy throughout England, but its real stronghold is in the Cairngorms and Highlands. Falk's pics

...Doros profuges (77,-66%)

A distinctive, large and spectacular wasp mimic - but very elusive. It is believed to have a very short flight period in early June (late May). Larvae are believed to be associated with black ants - or the aphids they attend. The related (and even rarer) continental species D destillatorius was observed apparently ovipositing on a moss-covered oak at about head height, near an ant trackway up the tree. It is known from the central part of southern England, northern Lancashire and the Isle of Mull - but its elusiveness means it could easily be undetected elsewhere. Falk's pics

*TOP TARGETS*

...Anasimyia contracta (28,-79%), Eurimyia lineata (21,-83%) and Anasimyia transfuga (47,-98%)

These three are recognisable as Helophilines by the striped scutum, bend in the radial vein and unspotted eyes. They can be distinguished from others by the elongate bodies, abdomen pattern and orange antennae. To distinguish from each other one needs a picture of the face ideally in side profile (extended forwards into a snout in Eurimyia, and slightly extended in some Anasimyia), the shape of the second abdominal segment seen from above (try and get it with the wings open), and the pattern on T3-4 including the sides.

They can be found around wetlands and ponds with emergent vegetation to trap rotting material. E lineata is abundant everywhere, A. contracta appears to be missing in the north of Scotland, and A transfuga seems to be missing north of Yorkshire. Falk's pics

*TOP TARGET*

...Epistrophe diaphana (59,-96%)

One of two Epistrophe with black antennae, but unlike E. grossluariae the bands are pinched forwards at the margins like a Syrphus. It can be distinguished from Syrphus by the shinier scutum and yellower frons - not black at the front (especially obvious in females), also T5 is usually completely yellow (only yellow at the front and back edge in Syrphus).

The behaviour of this species is like other Syrphines and the larvae eat aphids. It is found in England as far north as Yorkshire, and is extending its range northward. Falk's pics

*TOP TARGET*

...Trichopsomyia flavitarsis (26,-99%)

A Pipizine hoverfly with the upper-outer cross vein joining the radial vein at a near right angle like a Pipizella (always get the wing venation with Pipizines!) The legs are much yellower than any Pipizella however. It has two spots on the abdomen like a Pipiza. T lucida has been recorded once in the UK - but the wing venation is different, and the abdominal spots are larger.

It is a species of wetlands/boggy areas. The larvae attack larvae of the psyllid Livia junci which make striking galls on rushes. T. flavitarsis is abundant throughout Great Britain. Falk's pics

*TOP TARGETS*

...Sphegina clunipes (20,-100%)* and *Sphegina sibirica (35,-92%)

Your best bet for getting identifiable pictures of Sphegina is to get very clear pictures of the wing venation, the feet (contrastingly black in sibirica) and the abdomen of a male from the side (the genital capsule of clunipes has a very prominent 'spike' pointing forwards on each side.) This is a challenge with such tiny, delicate flies.

S clunipes is one of the commonest hoverflies with no iNatUK observations. It is found everywhere in Great Britain, but sibirica is uncommon in England south and east of a bent line from Bournemouth to Birmingham to Hull. These species like lush vegetation in and around woods. They prefer shade - but less so in Scotland - and the larvae are associated with sap runs. Falk writes that adults can often be found nectaring on Fool's Watercress and Lesser Water-Parsnip. Falk's pics

*TOP TARGETS*

...Xylota jakutorum (29,-91%), Xylota xanthocnema (59,-87%)

Xylota species are usually observed running around on broad leaves: they are not often seen on flowers. Useful characters include the abdomen markings, the colour hind tibia from the side (the view from above can be deceptive because yellow hairs can mask the black colour of the apical part), the dust spots on the female frons and the shape of the abdomen (from above). xanthocnema is restricted to England and Wales, jakutorum occurs north of a bent line from Bournemouth to Birmingham to Hull.

...Eristalis cryptarum (66,-94%)

Only found in association with bogs on Dartmoor. A distinctive reddish appearance for an Eristalis and mostly orange legs. Falk's pics

...Eumerus sabulonum (51,-100%)

The easiest Eumerus to identify because the sides of T2 are reddish. This is a strongly coastal species, appearing on the west coast of Britain from Portsmouth to Glasgow, especially Wales. Larvae may be associated with Sheep's-bit (Jasione montana) Falk's pics

...Eumerus ornatus (51,-97%)

This Eumerus requires a very clear picture of the position of the ocellar triangle on the vertex. It occurs mainly in certral and southern England, but extends into south and north Wales and up the coast to the Peak district, and in the east to Lincolnshire. It is associated with meadowsweet (Filipendula ulmaria) Falk's pics

...Mallota cimbiciformis (56,-92%)

A furry bumblebee mimic in the tribe Eristalini, subtribe Helophilina, so the radial vein is strongy bent but the marginal cell is open. The scutum is densely golden haired, the black abdomen is sparsely white haired. The wing has a central cloud. This is another species whose larvae are associated with water-filled rot holes in mature deciduous broadleaved trees. It is most concentrated it the south of England, but there are scattered records as far north as Montrose. It does not seem to occur in Wales, however. Falk's pics

The following species were discussed in May's's 'First month you may find', but they peak now:

Brachypalpoides lentus (36,-79%), Chrysotoxum arcuatum (22,-81%), Chrysotoxum cautum (34,-53%), Eupeodes nielseni (73,-100%), Hammerschmidtia ferruginea (74,-100%), Lejogaster metallina (12,-96%), Microdon analis (70,-84%), Microdon devius (52,-100%), Parhelophilus frutetorum (37,-93%), Pipiza austriaca (40,-92%), and a summary of various *Platycheirus

The following species were discussed in April's's 'First month you may find', but they peak now:

Parasyrphus annulatus (71,-100%)

Other species that peak in June [species in square brackets usually require microscopy to identify]:

Pipizinae [Heringia brevidens (90,-100%), H. (75,-100%), H. vitripennis (69,-93%)]
[Pipiza fasciata (74,-100%)]
[Pipizella viduata (17,-99%), Pipizella virens (42,-98%)]
Microdontinae [Microdon mutabilis (50,-94%), M. myrmicae (63,-62%)]
Eristalinae Chalcosyrphus nemorum (23,-80%)
[Cheilosia ahenea (95,-100%), C. sahlbergi (92,-100%), C. vicina (47,-100%)]
Chrysogaster virescens (41,-100%)
[Melanogaster hirtella (9,-97%)]
Merodon equestris (10,169%)
Orthonevra intermedia (93,-100%), O. nobilis (32,-90%)
Pelecocera scaevoides (64,-100%)
Sericomyia lappona (23,-77%)
Riponnensia splendens (26,-70%)
[Sphegina. elegans (33,-94%), S. verecunda (36,-99%)]
Tropidia scita (15,-71%)
Volucella bombylans (5,-42%), V. inflata (31,-38%)
Syrphinae Chrysotoxum octomaculatum (87,-100%), C. vernale (85,-72%)
[Dasysyrphus friuliensis (80,-100%), D. neovenustus (87,-68%), D. pinastri (60,-91%)]
Eupeodes lundbecki (93,-100%)
Lapposyrphus lapponicus (79,-82%)
Melangyna ericarum (90,-100%), Melangyna labiatarum (43,-61%)
Meliscaeva auricollis (15,63%)
Paragus albifrons (85,-100%)
Parasyrphus vittiger (48,-97%)
Platycheirus amplus (83,-100%), P. angustatus (14,-99%) P. europaeus (40,-100%), P. fulviventris (29,-97%), P. immarginatus (48,-100%) P. melanopsis (82,-100%), P. perpallidus (57,-100%), P. podagratus (46,-100%), P ramsarensis (40,-100%), P scambus (31,-96%), P. scutatus (14,-84%)
[Sphaerophoria batava (53,-100%), S. philanthus (22,-100%), S. potentillae (87,-100%), S virgata (69,-100%)]
Xanthogramma pedissequum (18,26%)
Xylota segnis (4,-43%)

June may be the first month you see...

...Eristalis rupium (38,-71%)

61%opa in June. An Eristalis with a distinct wing cloud (usually linear in males, like E horticola but the spots are pointy not rounded; quadrate in females). The hind metatarsus is yellow, unlike any other Eristalis except the distinctive E cryptarum which has almost entirely orange legs, and only occurs on Dartmoor. E rupium's stronghold is in Scotland and the very north of England, but it's range extends down the east coast as far as the Humber estuary, and down the Pennines to the Peak Distict. It is also fairly abundant in Wales, especially the northwest. Falk's pics

...Lejops vittatus (67,-100%)

72%opa in June. A Helophiline distinguished from the similar Anasimyia species by black, rather than orange andtennae, but in any case with a distinctive 'dashed' abdomen pattern. It's range is very limited: it occurs in coastal areas from Kent to Norfolk, and around the Severn estuary - venturing further inland on the Somerset Levels. It occurs in somewhat brackish waters - e.g. coastal grazing marsh - where the bases of sea clubrush (Scirpus maritimus) are normally submerged. The association with this plant is strong and the adults are said to be sluggish - not flying a lot - so searching and sweeping clubrush is the best way to find it. Falk's pics

...Chrysogaster cemiteriorum (29,-90%)

36%opa in June. This species has pale yellow wing bases and brownish antennae but the best feature if you can get it, is the strongly dusted proepimeron (side of the thoax just above the front coxae) - an image low to the side focussed on the area above the front leg is needed. It occurs throughout England and Wales to the south of Scotland, and also in the north of Scotland. Wetland, wet meadow and forest margins are the places to look, often found on umbellifers.

...Cheilosia scutellata (36,-77%)

53%opa in June. Several Cheilosia (including particularly this one) are helped by an image of the face knob from directly above - so try to get a shot of it down between the antennae to show whether it is pointed or rounded, narrow or broad. This is one of three UK Cheilosia in the subgenus Eucartosyrphus: their larvae feed in fungi (in this case members of Boletus), and they can be distinguished from other subgenera by the fact that the females have a pale tip to the scutellum. Common in England and Wales, but patchy in the very north of England and in Scotland. Falk's pics

Other species exceeding 10% of peak abundance (%opa) for the first time in June are [species in square brackets usually require microscopy to identify]:

Pipizinae Pipizella maculipennis (90,-100%) 25%opa
Eristalinae Blera fallax (77,-100%) 56%opa
Callicera aurata (67,-40%) 64%opa
[Cheilosia cynocephala (71,-100%) 25%opa, C. (50,-100%) 35%opa, C. velutina (76,-100%) 13%opa]
Chrysogaster solstitialis (12,-52%) 67%opa
Helophilus trivittatus (17,-18%) 45%opa
Pelecocera tricincta (66,-55%) 76%opa
Volucella pellucens (4,+78%) 89%opa, V. zonaria (16,+1034%) 17%opa
Xylota florum (48,-95%) 76%opa
Syrphinae Chrysotoxum bicinctum (10,-31%) 83%opa, C. festivum (27,+63%) 62%opa, Chrysotoxum verralli (46,+23%) 29%opa
Didea alneti (87,-100%) 50%opa
Epistrophe grossulariae (13,-8%) 39%opa
Eriozona syrphoides (40,-64%) 14%opa
Leucozona glaucia (11,-33%) 12%opa, L. laternaria (25,-56%) 54%opa
Melangyna umbellatarum (35,-61%) 34%opa
Meligramma guttatum (76,-100%) 38%opa
Paragus tibialis (70,-100%) 45%opa
Scaeva pyrastri (7,+18%) 40%opa
Sphaerophoria loewi (85,-100%) 75%opa
Xanthogramma stackelbergi (71,-15%) 67%opa

Posted on February 08, 2024 12:02 AM by matthewvosper matthewvosper | 0 comments | Leave a comment

February 07, 2024

What to look out for: May

[For explanations and definitions see here. Almost all of the data here is derived from NBN Atlas and the species information from Steven Falk's Flickr and the HRS website]

May is the first really big month for hoverflies, with 72 species at peak: only June has more. On top of that, a whopping 94 species exceed 10%opa for the first time! It's an important month for Criorhina/Matsumyia, Cheilosia, Brachyopa, Neoascia, Epistrophe, Parasyrphus, Heringia and Pipiza in particular - see the advice on how to photograph 'black jobs' in April's post.

Prominent among the species that are just getting going this month are members of Platycheirus, Chrysotoxum, Parhelophilus, Sphegina and other Brachyopini.

May is the best month to see....

*TOP TARGET*

...Callicera rufa (62,-70%)

A distinctive Callicera, dark with foxy red hair and legs entirely orange except the apical tarsal segements. This species was long known only from Caledonian pine forests, where the larvae inhabit rot holes in Scots pine but in the the last two decades it has begun to pop up all over England! They have also been found in other species of conifer. Falk's pics

*TOP TARGET*

...Brachypalpus laphriformis (42,-96%)

A well built and hairy species similar to Chalcosyrphus eunotus, but with shining scutum and without grey spots on the abdomen. Best found basking on tree trunks and stumps. The larvae develop in decaying tree wood, mainly beech and oak. Falk's pics

*TOP TARGET*


...Cheilosia bergenstammi (19,-97%) and Cheilosia fraterna (28,-95%)

Perhaps surprisingly underrecorded, although they are a little tricky to identify due to their similarity with each other! The following features help to distinguish this pair from other Cheilosia: orange antennae, black eye hairs, and face profile from the side (low facial knob). To distinguish from each other, in bergenstammi the hind leg has an obvious dark ring (fraterna usually doesn't), the scutellum has long marginal bristles (shorter in fraterna), and the body hair of bergenstammi is longer. These are the sorts of features that will get at lot of other Cheilosia to species. bergenstammi is associated with ragwort (jacobaea vulgaris) - the larvae mine the base of the stem. fraterna is associated with marsh thistle (Cirsium palustre). Look for ovipositing females on these plants regardless of whether they are flowering. Falk's pics of bergenstammi and fraterna

*TOP TARGETS*


...Criorhina asilica (49,-92%) Criorhina floccosa (31,-62%) and Matsumyia berberina (24,-87%)

Bumblebee mimics with a pointed face and distinctive shaped antennae. HRS still includes berberina in Criorhina. A good view of the tufts of hair on the side of the thorax is useful. These species are associated with rotting stumps of deciduous broadleaved trees. They can sometimes be found resting on the underside of leaves at a good height. Falk's pics

...Dasysyrphus venustus (19,-96%)

This is one of a group of quite difficult species to identify (well... all the Dasysyrphus except albostriatus and tricinctus). If you see a Dasysyrphus with the distinctive long dark Dasysyrphus stigma, and the curvy spots of this group it helps to show clearly whether the abdominal bands reach the margin, how extensive the face stripe is, the dusting on the frons, and if possible the underside of the abdomen. It can be found visiting a variety of flowers (Falk suggests in particular, buttercups, umbellifers and rowan). Falk's pics

...Melangyna arctica (54,-100%)

Similar to M lasiophthalma but less hairy. As with all Melangyna, try to get a good image of the scutellum (yellowish centre, with dark hind edge and corners). To distinguish from M lasiophthtalma and M ericarum, it helps to see the dark halteres, and the frons which is strongly dusted but the dust is darker than on the face. In males the hair on the scutum is black. Larvae are known to feed on the common alder aphid Pterocallis alni - so watch out for it around alder trees. Recent records suggest it has disappeared from the south east, it now occurs in Britain north and west of the Fosse Way (seriously... a diagonal line from Lincoln to Exeter!). Falk's pics

...Heringia latitarsis (75,-100%)

One of the few identifiable Heringia in photos, just - but you need a male and a good shot of the front leg. It's also very rare. The male has quite a strongly expanded front basitarsus. England and Wales. Larvae are associated with poplar aphids, but not exclusively. Falk's pics

...Platycheirus manicatus (9,-92%) and Platycheirus tarsalis (32,-78%)

It's hard to know why these species are quite so underrecorded. manicatus is one of the easiest Platycheirus to identify, with its snouted face, large spots and heavily dusted frons and scutum. It is very common everywhere. tarsalis is another snouted species, distinguished by the size of the markings and extent of dusting, as well as the number of expanded segments in the male foretarsi.

Their long mouthparts mean that they can feed on some tubular flowers that are not favoured by most hoverflies, such as ground-ivy and bluebells. Larvae are usually found in low vegetation: In general, low vegetation and long grasses are good places to look for Platycheirus. Falk's pics of manicatus and tarsalis

...Brachyopa bicolor (70,-100%), Brachyopa insensilis (60,-48%), Brachyopa pilosa (54, -100%) and Brachyopa scutellaris (38, -92%)

It is the month of Brachyopa - all four species at peak. The colour of the scutellum and the humeri (front corners of the thorax) are useful. The real clincher is the inside face of the antennae - a very hard shot to get in the field, but if you have a good macro camera give it a go! Half the problem is recognising them as hoverflies!

Brachyopa are stongly associated wth sap runs in old trees - which is where the larvae live. bicolor is most associated with Beech and Oak, and occurs south of Leeds (although its range is apparently expanding rapidly). insensilis used to be associated with elms until Dutch elm disease, but seems to have made the switch to horse chestnut - bringing it into more urban areas. pilosa is found south of Leeds and in the Cairngorms area: in Scotland it prefers aspen, poplar and birch, elsewhere it prefers oak and beech. scutellaris occurs throughout Britain and has a wide taste in trees Falk's pics

...Orthonevra brevicornis (44,-98%), and Orthonevra geniculata (45,-98%)

More black jobs... Wings and face will get you the genus, a good (side) view of the antennae and legs in addition will get you the species. brevicornis has normal-shaped antennae, the other three species have a very long final antennal segment. geniculata has partly yellow legs - a feature only shared with intermedia which is confined to Cheshire/Liverpool/Manchester - but geniculata has a stigma that is basally dark and an infuscated crossvein r-m (all pale stigma and uninfuscated r-m in intermedia). (The fourth, and commonest species, nobilis is identified by the combination of elongate antennae and black legs)

Apart from intermedia, British Orthonevra can be found all over Britain. They are associated with wetlands, fens, peat, carr etc. Falk's pics (no intermedia)

Eristalis abusiva (16,-98%)

This species closely resembles E arbustorum so everything here will also improve your ID rate on that common species. I wrote a guide on how to distinguish them here. It is important to get the middle tibia from the side (not black at the tip like arbustorum), and the face.

This species can occur anywhere but is commonest near the coast. Coastal grazing marsh is popular with it - look near muddy pools - and it likes to nectar on umbellifers and asters, including sea aster. Falk's pics

The following species were discussed in April's's 'First month you may find', but they peak now:

Chalcosyrphus eunotus (60,-95%), Cheilosia chrysocoma (53,-79%), Cheilosia pagana (11,-73%), Ferdinandea cuprea (18,-40%), Neoascia meticulosa (27,-95%), Neoascia obliqua (49,-95%), Pocota personata (66,-94%), Meligramma cincta (41,-52%), Parasyrphus malinellus (63,-100%), Pipiza luteitarsis (49,-86%)

Other species that peak in May [species in square brackets usually require microscopy to identify]:
Eristalinae Anasimyia interpuncta (62,-100%)
Caliprobola speciosa (68,-100%)
Cheilosia variabilis (20,-78%), [Cheilosia albitarsis (11,-99%), Cheilosia antiqua (33,-100%), Cheilosia barbata (55,-100%), Cheilosia griseiventris (73,-100%), Cheilosia lasiopa (57,-96%), Cheilosia nigripes (82,-100%), Cheilosia pubera (59,-100%), Cheilosia ranunculi (61,-100%), C. semifasciata (42,-100%), C. urbana (53,-100%), C. uviformis (95,-100%)]
Eristalis similis (88,+155%)
[Heringia heringi (64,-72%), H. pubescens (76,-100%), H. senilis (92,-100%), H. verrucula (85,-100%)]
Leucozona lucorum (8,-50%)
Portevinia maculata (23,-66%)
Psilota anthracina (79,-80%)
Rhingia campestris (2,-71%)
Xylota abiens (67,-100%)
Syrphinae Baccha elongata (13,-32%)
[Dasysyrphus hilaris (79,-82%)]
Epistrophe eligans (10,+45%), E. melanostoma (92,+473%), E. nitidicollis (53,-25%), E. ochrostoma (100,-100%)
Epistrophella euchroma (77,36%)
Melanostoma scalare (2,-48%)
Meligramma trianguliferum (61,-26%)
Parasyrphus nigritarsis (62,-84%)
Platycheirus sticticus (73,-100%), P. splendidus (55,-93%)
Sphaerophoria bankowskae (95,-100%)
Syrphus nitidifrons (100,-100%)
Xanthogramma citrofasciatum (43,-47%)
Pipizinae [Pipiza bimaculata (85,-100%), P. noctiluca (25,-93%), P. notata (51,-100%)]

May may be the first month you see...

...Hammerschmidtia ferruginea (74,-100%)

33%opa in May. If you live in or visit Strathspey in May or June that is where this large, unique and critically endangered hoverfly lives. You have a genuine chance of seeing it in the area between Grantown-on-Spey and Kingussie. It looks a bit like a Brachyopa, but larger and redder. It is associated with the rotting trunks/stumps of fallen aspen trees, but needs a significant area of aspen woods (about 4.5ha to thrive). Smaller woods are much less likely to yield the species. Falk's pics

*TOP TARGETS*

...Parhelophilus consimilis (55,-100%) , Parhelophilus frutetorum (37,-93%), Parhelophilus versicolor (33,-100%)

53%opa, 38%opa, and 59%opa in May respectively. It is difficult to get this genus to species. A good view of the front tibia will get you consimilis (black at the tip); your best bet for the other two is to get a low angle on the hind tibia - male frutetorum have a prominent tubercle at the base of the underside of the hind femur, versicolor does not. Remember, male Parhelophilus have well-separated eyes!

frutetorum does not occur in Scotland, the others occur everywhere. consimilis is easily the rarest. They are wetland specialists; consimilis is a particular fan of bogs and poor quality fen. Falk's pics

*TOP TARGET*

...Brachypalpoides lentus (36,-79%)

81%opa in May. Looks like a Xylota, or Chalcosyrphus, but the legs are entirely black and the abdomen mostly blood-red. The only other species with this combination is Chalcosyrphus piger, which was only added to the British list from Suffolk in 2021 - so take extra care there (the abdomen of C. piger is red to the tip - black at the tip in B lentus). Xylota segnis looks similar, but the band on the abdomen is smaller and more orange, and the legs are partly pale.

B lentus can be found anywhere in Britain, with NW England from Cheshire to Cumbria being a particular hotspot. Found flying through low undergrowth, larvae develop in rotting heartwood of living trees - especially Beech, and also perhaps oak. Look for trees with rot exposed close to the ground. Falk's pics

*TOP TARGETS*


...Lejogaster metallina (12,-96%), and Lejogaster tarsata (36,-97%)

39%opa and 27%opa respectively in May. As with other 'black jobs' in Brachyopini the face helps enormously to confirm the genus. In this case the shape and colour of the antennae are also crucial for the species determination. These are wetland species that are fond of buttercups. Both occur widely across Britain. Falk's pics

*TOP TARGET*

...Pipiza austriaca (40,-92%)

25%opa in May. This Pipiza is identifiable in both both sexes with a low angle on the hind femur. The hind femur is swollen, with a noticable ridge on the underside. Larvae feed on aphids, often on hogweed. According to Falk it is usually encountered on buttercups and umbellifers in meadows and at woodland edge. Falk's pics.

...Cheilosia impressa (25,-81%)

47%opa in May. A Cheilosia with yellow wing bases and entirely black legs, the eyes are also more brightly red than the C albitarsis complex, which also have yellow wing bases (but not entirely black legs - yellow forebasitarsi). Found around scrub and woodland edge, the adults are especially fond of umbellifers, the larvae mine the stems of burdock plants, so look for ovipositing females there. found all over the UK, but primarily in England and Wales.

...Microdon analis (70,-84%) and, Microdon devius (52,-100%)

61%opa and 16%opa respectively in May. These are the two species of Microdon with black rather than orange scutellum. They are distinguished by the color of hairs on the back half of the scutum - this feature is best photographed a little from the side, top down photos don't often show hair colour well.

These species are very restricted in range: analis is known from parts of the Highlands and Cairngorms, the area around Loch Linnhe and the Isle of Mull, as well as a triangle between Poole harbour, Oxford and London. devius is known in areas just south of London and towards the Solent (with a hotspot in the Surrey hills west of Dorking), another line from Oxfordshire east through the Chilterns, in East Anglia between Thetford and Eye, and in north-west Wales along the rivers Dwyryd and Mawddach. Both species are associated with heathy woodland, although devius also likes chalky grassland. They do not visit flowers but can be seen on low vegetation. M analis develop in the nests of black ants in the genus Lasius near rotting timber, whereas M devius prefers the distinctive nest mounds of the Yellow Field Ant Lasius flavus. The larvae look like hemispherical daleks... they're quite cool. (Incidentally the other two species can only be identified to species as larvae! They occur south of the M4, in the south-west peninsula, Wales and west Scotland from north of Glasgow to Mallaig - especially the Isle of Mull) Falk's pics

...Platycheirus

Twelve species of Platycheirus exceed 10%opa for the first time in May - including many of the clypeatus and peltatus groups (see list below). As clear a view of the abdomen and the legs - especially every part of the male front leg, is vital. Grassy wetland areas are a common theme, though P europeaus prefers woodland (especially with conifers); P. immarginatus prefers brackish habitats, saltmarsh, coast and tidal estuary, likes to visit sea clubrush, sea lavenders and sea couch; other meadow-like habitats are also frequented. They are good candidates for sweeping long grasses with a net. Falk's pics

...Chrysotoxum arcuatum (22,-81%) , Chrysotoxum cautum (34,-53%), Chrysotoxum elegans (51,-97%)

86%opa, 81%opa and 18%opa respectively in May. A low side angle provides easy identification of male cautum because of the large genitalia. In general with Chrysotoxum get the clearest photo of the antennae you possibly can - ideally from the side - so that the relative sizes of the segments can be seen. for some species the details of the abdomen pattern are useful - especially towards the sides. Undersides can also help.

Draw a line from the Humber to the Severn estuaries and you will find cautum below it and arcuatum above it (with a bit of mixing in the middle, and cautum also in south Wales). elegans is strongly coastal from Pembrokeshire to Portsmouth, but also occurs in the Surrey Hills and East Anglia around Thetford. They tend to occur in grassy areas, and tend to fly low and fast. Falk's pics

Eupeodes bucculatus (63,-100%), Eupeodes nielseni (73,-100%), Eupeodes nitens (69,-100%)

50%opa, 88%opa and 43%opa respectively in May. If you see a female Eupeodes with the frons too black for luniger but too dusted at the sides for latifasciatus it may be one of these. It is easier to ID females. They are quite dark species: in nitens and neilseni the sides of the fifth tergite are almost entiely black, and female neilseni have an entirely black hind femur. With all Eupeodes it is valuable to show the abdomen pattern right to the edge, the female frons and face, and the underside is particularly useful if you can get it. Falk's pics

Other species exceeding 10%opa for the first time in May are [species in square brackets usually require microscopy to identify]:

Pipizinae [Pipizella viduata (17,-99%) 25%opa, P. virens (42,-98%) 37%opa]
Trichopsomyia flavitarsis (26,-99%) 14%opa
Microdontinae [M. myrmicae (63,-62%) 81%opa]*
Eristalinae Anasimyia lineata (21,-83%) 33%opa, A. lunulata (46,-98%) 14%opa, A. transfuga (47,-98%) 26%opa
Chalcosyrphus nemorum (23,-80%) 80%opa
Cheilosia illustrata (7,-29%) 16%opa, C. soror (45,-44%) 15%opa, [C. vicina (47,-100%) 22%opa, C. vulpina (47,-93%) 69%opa]
Chrysogaster virescens (41,-100%) 48%opa
Eristalinus sepulchralis (14,-67%) 29%opa
Eristalis arbustorum (3,-41%) 22%opa, E. horticola (10,-56%) 36%opa, E. nemorum (9,-24%) 40%opa
Eumerus sabulonum (51,-100%) 22%opa, [E. strigatus (30,-99%) 50%opa]
Helophilus hybridus (16,-63%) 38%opa, H. pendulus (0,-24%) 39%opa
Melanogaster aerosa (58,-100%) 14%opa, M. hirtella (9,-97%) 31%opa
Merodon equestris (10,+169%) 55%opa
Myathropa florea (4,+174%) 50%opa
[Myolepta dubia (71,-74%) 10%opa, M. potens (92,-100%) 50%opa]
[Neoascia geniculata (39,-98%) 70%opa, N. tenur (5,-99%) 32%opa]
Orthonevra nobilis (32,-90%) 15%opa
Riponnensia splendens (26,-70%) 24%opa
Sericomyia lappona (23,-77%) 88%opa, S. silentis (3,-48%) 11%opa
Sphegina sibirica (35,-92%) 24%opa, [S. clunipes (20,-100%) 39%opa, S. elegans (33,-94%) 13%opa, S. verecunda (36,-99%) 24%opa]
Syritta pipiens (2,-37%) 25%opa
Tropidia scita (15,-71%) 44%opa
Volucella bombylans (5,-42%) 18%opa, V. inflata (31,-38%) 31%opa
Xylota jakutorum (29,-91%) 17%opa, X. segnis (4,-43%) 60%opa, X. sylvarum (17,-41%) 12%opa, Xylota tarda (68,-100%) 27%opa
Syrphinae C. octomaculatum (87,-100%) 25%opa, C. vernale (85,-72%) 50%opa
Dasysyrphus friuliensis (80,-100%) 57%opa, D. neovenustus (87,-68%) 14%opa
Didea intermedia (65,-83%) 35%opa
Epistrophe diaphana (59,-96%) 43%opa
Episyrphus balteatus (0,45%) 14%opa
Eupeodes corollae (6,39%) 19%opa
Megasyrphus erraticus (58,-88%) 50%opa
Melanostoma mellinum (3,-88%) 48%opa
Paragus albifrons (85,-100%) 33%opa, [P. haemorrhous (18,-97%) 31%opa]
Parasyrphus lineola (57,-73%) 81%opa, P. vittiger (48,-97%) 31%opa
Platycheirus amplus (83,-100%) 20%opa, P. angustatus (14,-99%) 30%opa, P. aurolateralis (88,-100%) 33%opa, P. clypeautus (8,-99%) 37%opa, P. europaeus (40,-100%) 46%opa, P. fulviventris (29,-97%) 25%opa, P. immarginatus (48,-100%) 20%opa, P. nielseni (37,-100%) 19%opa, P. occultus (29,-99%) 28%opa, P. peltatus (22,-96%) 74%opa, P. podagratus (46,-100%) 36%opa, P. scambus (31,-96%) 25%opa
Pyrophaena granditarsis (7,-93%) 13%opa, P. rosarum (15,-90%)
27%opa

Scaeva selenitica (37,-9%) 19%opa
Sphaerophoria rueppellii (44,-64%) 17%opa, S. scripta (5,+25%) 14%opa, [S. batava (53,-100%) 27%opa, S. fatarum (58,-96%) 28%opa, S. interrupta (56,-96%)
30%opa, S. philanthus (22,-100%) 27%opa, S. taeniata (65,-100%) 23%opa]

Xanthogramma pedissequum (18,+26%) 41%opa

Posted on February 07, 2024 11:46 PM by matthewvosper matthewvosper | 0 comments | Leave a comment

What to look out for: April

[For explanations and definitions see here. Almost all of the data here is derived from NBN Atlas and the species information from Steven Falk's Flickr and the HRS website]

April is a significant month for hoverflies: Only 11 species are at their peak, but more than 80 are on the rise! It's very much the start of Rhingiini season, with 5 species of Cheilosia at their peak and another 18 getting off the mark, as well as every species in Rhingia, Portevinia and Ferdinandea. Most Pipizines in Pipiza, Herigia and Neocnemodon get going this month too; so make sure you're paying attention to the 'black jobs'.

Advice for getting identifiable pictures of 'black jobs': Some can be identified reasonably easily - but the lack of an abdomen pattern is a hinderance and many realistically require microscopy. Here's how to give yourself the best chance, even with the difficult ones. The face (including side profile), antenna shape and colour, and legs (especially the front tarsi and hind femur) are especially useful. The colour of hairs on the abdomen, scutum, face and legs sometimes play a role - this may be best obtained from the side (or at least not directly from above) so that light shines through the hairs. Wing venation is very useful for getting Pipizines to genus. For Cheilosia small hairs on the sides of the face may be important, and it is often important to know whether the eyes are hairy. For a few Cheilosia (Nr. proxima) it is necessary to turn them over and get the underside of the abdomen (this is also important for tiny Paragus species). If the fly is not in a position to see the underside, catching it in a spi-pot is a useful approach.

April is the best month to see....

*TOP TARGET*

...Platycheirus ambiguus (56,-85%)

A grey-marked Platycheirus, but the only one in which the female is banded rather than spotted, and the only one in which the male foreleg is not expanded in any way (it does have a curled bristle on the back of the front femur near the knee - so try to get one focussed on that knee if you suspect ambiguus. The male frons is very broad and well dusted.

This species is strongly associated with blackthorn. You may see it it hovering near blossoms at 1-4m height. Found throughout Great Britain. Falk's Images

*TOP TARGET*

...Cheilosia nebulosa (65,-76%)

A somewhat furry Cheilosia with a vague dark smudge across the centre and tip of the wing. The colour of the wing bases and scutum hairs can give it a bit of a golden sheen. The frons is rather swollen. The legs are extensively pale, but the femora are black. The antennae are orange, but not excessively bright or large. See Falk's pictures

This species is rather rare but widespread, and can be found in Great Britain as far north as the central belt of Scotland. The specific larval habitat is unknown but the adult is associated with carr (waterlogged woods) and marsh habitats. It can be seen on Salix catkins and hawthorn. If you see it ovipositing that would be amazing!

*TOP TARGET*

...Parasyrphus punctulatus (30,-68%)

Our earliest Parasyrphus to peak, and relatively easy to identify. It is best found basking on or hovering near tree foliage - so look up sometimes! Its tastes are wide ranging,but it is usually found in wooded areas, particularly if conifers are present. Throughout Britain and Ireland. Falk's pics

The following species were discussed in March's 'First month you may find', but they peak now:
Cheilosia albipila (44,-79%), Cheilosia grossa (38,-59%), Criorhina ranunculi (35,-71%), Melangyna barbifrons (75,-100%), Melangyna lasiophthalma (25,-81%), Platycheirus discimanus (85,-43%)

Other species that peak in April [species in square brackets usually require microscopy to identify]:
Cheilosia caerulescens (79,+331%), [C. psilophthalma (88,-100%)]

April may be the first month you see...

*TOP TARGET*

...Pocota personata (66,-94%)

43% of peak abundance (%opa) in April. Possibly the best of the bumblebee mimics! Distinctive with its peculiarly small head and droopy orange antennae. A rare species associated with old woodlands and parklands. It seeks rot holes in mature trees, perhaps especially beech, but also Sycamore and Ash. They can easily be mistaken for tree bumblebees entering a high nest. Searching such trees is said to be the best way to find it. Occurs in England as far north as Durham - you might just see one in Wales near the border. Falk's pics

*TOP TARGETS*


...Ferdinandea cuprea (18,-40%) and Ferdinandea ruficornis (65,-100%)

37%opa and 20%opa in April respectively. Ferdinandea are easily recognisable by their metallic sheen, dust-striped scutum, orange antennae, bristly scutum and scutellum marins, and sharply infuscated inner cross veins. F ruficornis is rarer, and harder to confirm from photos. F cuprea has a more golden appearance than the darker F ruficornis; cuprea has small black spines on the backs of the front and middle tibiae - so it's worth trying to get sharp pictures of the legs. In ruficornis the aristae are red rather than black in cuprea - so a sharp picture of the antennae is useful. Falk's images

These more species associated with trees. The larvae live in sap runs, so woodland with old trees is a good place to look. They may bask on tree trunks. cuprea is common throughout Britain and Ireland.
ruficornis is found in England up to about Leeds, and on the north coast of Wales.

*TOP TARGETS*


...Neoascia interrupta (56,-96%), Neoascia obliqua (49,-95%) and Neoascia meticulosa (27,-95%)

All at 15%opa in April, but obliqua and meticulosa are rising quickly to their peaks in May. These are rather small flies, with abdomens strongly waisted. See Falk's images These are also the three easiest to identify. interrupta and obliqua are amongst the species with infuscated cross veins. interrupta is the only species with lateral spots on T4, obliqua usually has unique, oblique marking on the very narrow T2. meticulosa has very yellow legs. To give yourself the very best chance of identifying the other species of the genus (which all peak in July/August) a sharp side profile of the antennae and the hind knees might get you there. The real clincher is sometimes the underside of the thorax... but this is really hard with such small flies.

I'm unsure of the distribution in Ireland, but in Great Britain meticulosa and obliqua are ubiquitous, but interrupta is basically confined to England with a very small number of extreme outliers in northern Scotland. obliqua is strongly associated with butterbur, meticulosa and interrupta are associated with bulrushes. Falk's pics

...Chalcosyrphus eunotus (60,-95%)

23%opa in April. A well-built and hairy species with infuscated cross veins, most easily confused with Brachypalpus laphriformis, but also easily distinguished by the vague stripy scutum dusting (shiny in B laphriformis) and the grey patches on the second tergite. The larvae develop in partially submerged logs in streams in wooded areas, especially where log jams are formed, and they can be found exploring such logs or basking near the bank on logs or foliage. It is distributed in the west of England south of Liverpool, and the north coast and Marches of Wales. Falk's pics

...Cheilosia pagana (11,-73%)

70%opa in April. Very common, and the female is quite distinctive due to the large bright orange antennae. The male antennae are also orange, but less big and garish! It is important, especially with males, to show that the eyes are not hairy. The face knob is pointed and males lack long white hairs under the hind femur. Most likely to be confused with C soror. Larvae develop in Apiaceae such as cow parsley. Ubiquitous in Britain and Ireland. Falk's pics

...Cheilosia chrysocoma (53,-79%)

26%opa in April. A large and distinctive Cheilosia with dense, long, bright orange hair, orange antennae and infusated cross veins. Associated with damp woodland. Apparently it is most commonly observed resting on low vegetation. Larvae may be associated with wild angelica. Falk's pics

...Meligramma cincta (41,-52%)

48%opa in April. Easily identified by its combination of elongate shape, neat, straight-edged yellow bands, and sharp triangular markings on T2. Only Meliscaeva cinctella is similar, but in that species the T2 markings are blunt and the bands less straight-edged.

It is primarily (but not exclusively) associated with beech-containing woodland (the larvae feed on woolly beech aphids). It will often hover in shafts of light at 2-4m high. Falk's pics

...Parasyrphus annulatus (71,-100%) and Parasyrphus malinellus (63,-100%)

36%opa and 22%opa in April respectively. These two species are certainly rare and neither is yet recorded on iNat. A photo of the face and frons helps confirm the genus. With Parasyrphus, as with Syrphus, it is crucial to get a very clear picture of the hind leg. Hind tibia broadly yellow at the base but not the tip, and hind femur yellow at the base will confirm annulatus (also front tarsi truly yellow and large dst spots on the female frons). mallinellus is most easily confirmed under the microscope but would be confirmed by hind leg all black except broadly at the base of the tibia, front tarsi darker than tibiae, small dust spots on female frons and even better if you can get the small black triangular markings on the underside of the abdomen.

Parasyrphus are usually found in association with coniferous woodland. Records are spread throughout Great Britain. I do not know about Ireland. Falk's pics

...Pipiza luteitarsis (49,-86%)

27%opa in April. One of the few relatively easily identifiable species. The entirity of the front tarsi are yellow (in other species at least some segments are black). The body is yellow haired, the wings are clear and, like many other Pipiza, the abdomen often sports a pair of yellow spots.

The larvae feed on the aphid Eriosoma ulmi, which causes leaf curl on elm trees., so look for them near elm (or open the curled leaves and attempt to rear any larvae you find!!). May be found anywhere in Great Britain (I do not know about Ireland). Falk's pics

Other species exceeding 10%opa for the first time in April are [species in square brackets usually require microscopy to identify]:

Pipizinae [Heringia heringi (64,-72%) 32%opa]
[Neocnemodon brevidens (90,-100%) 50%opa, N. pubescens (76,-100%) 38%, N. vitripennis (69,-93%) 25%opa]
[Pipiza fasciata (74,-100%) 29%opa, P. lugubris (68,-93%) 17%opa, P. noctiluca (25,-93%) 22%opa, P. notata (51,-100%) 26%opa]
Microdontinae [Microdon mutabilis (50,-94%) 11%opa]
Eristalinae Anasimyia interpuncta (62,-100%) 11%opa
Brachyopa pilosa (54,-100%) 28%opa, B scutellaris (38,-92%) 13%opa
Cheilosia bergenstammi (19,-97%), 34%opa, C, mutabilis (63,-100%) 17%opa, C. variabilis (20,-78%) 16%, [C. antiqua (33,-100%) 11%opa, C. barbata (55,-100%) 19%, C. carbonaria (79,-100%) 20%, C. fraterna (28,-95%) 21%opa, C. griseiventris (73,-100%) 40%opa, C. lasiopa (57,-96%) 11%, C. latifrons (43,-100%) 22%opa, C. proxima (21,-97%) 21%opa, C. pubera (59,-100%) 31%opa, C. ranunculi (61,-100%) 30%, C. semifasciata (42,-100%) 63%opa, C. urbana (53,-100%) 62%opa, C. vernalis (21,-100%) 45%opa]
Criorhina floccosa (31,-62%) 13%opa
Eristalis intricaria (6,-43%) 31%opa, E similis (88,155%) 50%opa
[Eumerus funeralis (34,-96%) 11%opa]
Orthonevra geniculata (45,-98%) 37%opa
[Neoascia podagrica (7,-98%) 15%opa]
Portevinia maculata (23,-66%) 11%opa
Mallota cimbiciformis (56,-92%) 19%opa
Syrphinae Baccha elongata (13,-32%) 19%opa
Dasysyrphus albostriatus (20,+53%) 15%opa, D. tricinctus (24,-45%) 11%opa, [D. pinastri (60,-91%) 20%opa]
Didea fasciata (34,-45%) 15%opa
Epistrophe eligans (10,45%) 51%opa, E. melanostoma (92,+473%) 33%opa
Eupeodes latifasciatus (19,-55%) 16%, E. luniger (8,0%) 49%opa
Melangyna labiatarum (43,-61%) 18%opa, M. sexgutta (=compositarum) (49,-94%) 14%opa
Melanostoma scalare (2,-48%) 52%opa
Meligramma triangulifera (61,-26%) 23%opa
Meliscaeva cinctella (12,-49%) 11%opa
Platycheirus scutatus (14,-84%) 34%opa, P. splendidus (55,-93%) 76%opa, P. sticticus (73,-100%)
40%opa, P. tarsalis (32,-78%) 25%opa

Syrphus ribesii (3,-38%) 28%opa, [S. vitripennis (6,-99%) 15%opa]
Xanthandrus comtus (41,-69%) 10%opa

Posted on February 07, 2024 11:14 PM by matthewvosper matthewvosper | 0 comments | Leave a comment

What to look out for: March

[For explanations and definitions see here. Almost all of the data here is derived from NBN Atlas and the species information from Steven Falk's Flickr and the HRS website]

March is the month that hoverflies begin to get going. It's not exactly a bumper month (just 13 species in total qualify to be covered in this post), but hoverflies will get increasingly common and diverse as the month progresses - depending on the weather. Look especially at any Prunus species in flower - blackthorn is a particularly popular plant. But also inspect catkins and don't neglect common weeds like dandelions! There are a few underrecorded early Spring specialists to look out for though... many of these species are small elongate species like Melangyna, Melanostoma and Platycheirus.

March is the best month to see....

*TOP TARGET*

...Melangyna quadrimaculata (58,-72%)

This is the one and only UK hoverfly that actually peaks in March (so I've gone to town on it a bit!). This species can sometimes even be seen in February, and it remains abundant in April before almost disappearing. The species is underrecorded in iNatUK by 72% compared to the NBN database, and 58th centile for rarity, so quite a challenge but well worth looking for! Records are spread widely if patchily across the whole of Great Britain.

How to identify... You can see RG iNat observations here (inc. international) and Steven Falk's fabulous resource here. It is a thoroughly strange species for Syrphini due to its basically black scutellum and face; it is easily mistaken for a Platycheirus. Males have four obscure spots (as suggested by the scientific name) arranged as a pair on each of T3 and T4. Female abdomens are entirely black. The wing stigma is very long and black - reminicent of Dasysyrphus. The scutum bears long golden/pale hairs. The eyes are distinctly hairy. The legs and antennae are completely black.

Similar species...
Platycheirus males have modified forelegs, usually have spots on T2, coloured parts to the legs and bare eyes. The long black stigma of M quadrimaculata should also help to separate.
Cheilosia species are not so elongate, the head does not hug the thorax like in Syrphinae, and there are zygoma on the face. Some have orange antennae. None have a similar stigma.
Melangyna barbifrons is a similarly dark Melangyna that begins to occur a little in March and peaks suddenly in April. The eyes are not hairy, and the hairs on the male scutum are mostly black. Males have the same arrangement of spots as quadrimaculata but females have paired spots on all of tergites 2-4. The stigma is apparently much paler.

How to find...

Larvae apparently feed on adelgids (woolly-aphid-like creatures) associated with fir trees. So you need to be in an area with some conifers. If you see woolly material on a conifer, you might therefore encounter an ovipositing female. Adults can be found attending the catkins of Salix and hazel trees (though it might be worth checking other catkins too), they may also attend blackthorn flowers - one of the best plants for finding early hoverflies generally.

March may be the first month you see...

*TOP TARGETS*

...Cheilosia grossa (38,-59%) and Cheilosia albipila (44,-79%)

88% and 39% of peak abundance (%opa) in March respectively. Large, furry and distinctive Cheilosia species. When photographing furry Spring Cheilosia try to get the colour of the antennae and the femora. albipila has orange antennae and the female has entirely orange legs (black antennae and femora in grossa). Neither species has a wing cloud. Both species can be found anywhere in Great Britain. The larvae of grossa mine thistle stems, especially spear thistle, so look for ovipositing females at the base of these plants (not just nectaring on the flowers), adults nectar on a variety of flowers. albipila larvae mine marsh thistle stems, and are therefore associated strongly with wetlands. Here are Falk's pictures of albipila and grossa

...Platycheirus discimanus (85,-43%)

33% of peak abundance (%opa) in March. A grey spotted species. In males the foretibia is not expanded (unlike albimanus) - only the first two foretarsi are expanded into a disc shape: all other species like this have yellow spots. The male frons is quite broad. The female frons is broader than in albimanus and lacks the small lateral dusting of albimanus. The female fore- and mid- femora are black (yellow, sometimes darkly, in albimanus), and the female abdomen is spotted (banded in ambiguus). Most easily identified from males, but you need a good shot of the front feet! Found throughout Great Britain. Visits blackthorn blossom. Very rare though - would be a superb find! Falk's pics

...Eristalinus aeneus (30,-51%)

30%opa in March, although it doesn't peak until July, and can be found as an adult even in the winter. Eristalinus have unique spotty eyes. aeneus is a large species in which eye hairs are missing from the lower part of the eyes, and the scutum normally lacks distinct dust stripes. Males are easily identified because the eyes are connected as normal in hoverflies (not so in E sepulchralis). This is a coastal species; larvae live in brackish pools and may feed on rotting seaweed. Falk's pics

...Melangyna lasiophthalma (25,-81%)

28%opa in March. A common species, but quite underrecorded on iNat. It is widely distributed throughout the British Isles. It has a normal Melangyna pattern with three pairs of yellow spots, but it is hairier than most Melangyna. Be sure to get a good photo of the scutellum, and/or the female frons. The scutellum is mainly yellow, but has significantly black corners and the hind margin is narrowly black. The female frons has small dust spots compared to other well-marked species. See Falk's pictures. It can be found on Salix catkins and Prunus blossom, or basking on sunlit tree trunks.

...Syrphus torvus (13,-68%)

19%opa in March. High quality pictures of the eyes are required to show eye hairs, especially in females. Falk's pics

...Criorhina ranunculi (35,-71%)

15%opa in March. An impresssive bumblebee mimic which is quite easily identified and can be found anywhere in Great Britain. Get a good view of the antennae/face and the wing venation if possible. This species peaks in April and is rarely seen by June, it is most likely to be confused with Volucella bombylans, becuase it shares the pointy yellow face, but that species does not appear until May. Volucella species have an incurved upper-outer cross vein, and the antennae are distinctly different. C ranunculi has long pale hairs on the scutellum contrasting with a completely black-haired scutum: this combination would be most unusual in V bombylans. It could also be confused with Eristalis intricaria, but that has a loop in the radial vein, and lacks the pointy yellow face. Male C ranunculi have a swollen hind femur which separates it from both of the above species.

It hovers territorially to defend patches of blossom and is aggressive towards other insects. It prefers broadleaved wooded areas. Prunus species are popular, but it can also be found on catkins. It may be found resting on the undersides of leaves above head height or on tree trunks. Females may be seen ovipositing near the base of living trees suffering heart-rot. Falk's pics

...Melangyna barbifrons (75,-100%)

13%opa in March. See above for differentiation from M quadrimaculata. Very rare. There are no observations of M barbifrons on iNat anywhere in the world, but Falk has pictures of a female and a male from Norway is shown here. NBN and HRS maps differ slightly, but both show a wide distribution throughout the island of Great Britain. Falk's pics

Other species exceeding 10% of peak abundance (%opa) for the first time in March are [species in square brackets usually require microscopy to identify]:
Meliscaeva auricolis (15,+63%) 12%opa,
Parasyrphus punctulatus (30,-68%) 11%opa,
Eristalis tenax (1,+91%) 15%opa, E. pertinax (1,+57%) 14%opa

Posted on February 07, 2024 11:01 PM by matthewvosper matthewvosper | 1 comment | Leave a comment

February 01, 2024

State of the Syrphs - 1-Feb-2024

Hello all,

The award for first iNatUK hoverfly observation of 2024 goes to @kiteheights for this Eristalis tenax that was enjoying the view from a WWII gunsite at Lavernock Point Nature Reserve on Jan 6th. Congratulations, your prize is a warm glow!

This February we will undoubtedly reach 75,000 iNatUK hoverflies! Very nice :)

Problem with images

Early in January Google changed the ways in which images could be displayed from Googledrive, which prevented all the images I've posted to this project from showing (and mucked up an awful lot of other websites too). I've managed to fix it for the website, but I notice they are still not visible on the apps.

"What to look out for"

As mentioned previously I'm preparing some monthly resources to help us seek out a greater diversity of hoverflies by highlighting seasonal species that are currently very underrecorded on iNat. Obviously what is 'seasonal' is based on an overall view - spring species will be slightly earlier in the south than the north, so bear that in mind. I'm not doing one for February specifically, because there aren't any species that meet the requirements for inclusion that early in the year. Also, I want to write every month and post them all at once. If you want to get ahead of the game, when the March article is published it will be here.

Identifications

It's great to see that over the winter we have consistently been adding far more identifications than were added in the two years before the project started.

While the number of observations does increase each month from now until July, it doesn't really take off until April - so we have two more months to reduce the NeedsID pile further before floods of new observations start arriving. I would love to think we could get the total number needing ID down below 1/2 of its peak last year - it peaked at just over 17000, so that's a target of below 8500. Very doable I think.

Here's what we currently face: (incidentally, a tip for reading these if you're not sure what the smaller genera are - the Syrphini genera are in alphabetical order from bottom to top, the tribes are also in alphabetical order but grouped by subfamily. This is also the order of the legend from left to right - but the names written on the bars are omitted from the legend)

As you can see we didn't make as much progress this month as in December, but that's hardly surprising with many of us being back to work.

Still, only 8 genera increased in numbers (not by much), 21 remained unchanged and 41 were reduced. The biggest fallers (with >50obs to start with) were Merodon (-64%), Pipizella (-41%), Neoascia (-26%), Eupeodes (-25%), Rhingia (-25%), Scaeva (-22%), Eumerus (-14%), Melanostoma (-11%), Pipiza (-11%), Melangyna (-10%), and Xylota (-9%). There is some correspondence with the genera that were specified in the latter part of the 'Twelve Syrphs of Christmas' event.

The genera still with more than 100 observations needing ID are: Eupeodes (1395), Platycheirus (1394), Eristalis (1325), Melanostoma (978), Cheilosia (606), Helophilus (254), Syrphus (243), Xylota (220), Epistrophe (130), Chrysotoxum (124), and Neoascia (107).

Annotations

An unsurprisingly small number of observations were uploaded in January, and we maintained a high level of annotation.

Overall, the proportion of UK observations with a sex annotation has continued to rise steadily.

Obscured Locations

A higher proportion of obscured locations this month, but this is not too much of a concern because that proportion is always likely to be volatile when the total number of observations is so small. (It represents just 11 observations)

Hope you have a fine February.

All data compiled on 31/01/2024

Posted on February 01, 2024 09:46 AM by matthewvosper matthewvosper | 0 comments | Leave a comment

January 20, 2024

Improving the Diversity of Hoverflies on iNatUK: Introducing "What to look out for"

One of the things that makes iNatUK's data less useful for the HRS than it might be is that there is a very strong bias towards a small number of charismatic, large and easily identified species. This is inevitable with citizen science to a degree, but doing something about it sounds like a fun challenge for us all!

To help us improve the diversity of what we observe, I have been sifting through the hoverfly records held by the NBN atlas and I plan to produce a post for each month entitled "What to Look Out For" in which I will highlight some of the seasonal species that are underrecorded in iNaturalist, but which should be identifiable from photos and are common enough to hope we could find. I intend that this will include information on how and where to find them, as well as how to identify them.

To flesh out the scale of the challenge a bit: by comparison with the more comprehensive NBN atlas database only 22 species are overrecorded on iNat! This leaves 251 species underrecorded, of which 86 have 0 observations on iNat.

One simple and general way we could improve our hoverfly diversity is by paying more attention to hoverflies in the first half of the year. Here's why I say this: The top 10 species in iNat (accounting for nearly 50% of all observations) include just one that peaks before July (and only four of the top 20) - but nearly 60% of UK species peak before July!!!

In each "What to look out for" I will list the species that are at peak abundance that month in a section called "MMM is the best month to see...", and I will also list species that are starting to increase significantly (first month at >10% of peak abundance) in a section called "MMM is the first month you might see...". I will choose a few species from each section to highlight with more information so that we can look for them intelligently - but you will also be able to look through the rest of the list for other suitable candidates. The choice of what to highlight will be based on a combination of 1) How underrecorded is the species on iNat? 2) How rare is the species? (i.e. is it realistic to think we might find some?) 3) How identifiable is it from photographs?

To each species I have attached a pair of numbers: e.g. Eristalis tenax (1,91%). The first number is the rarity expressed as a centile of abundance according to NBN: a low number suggests a common species, a number close to 100 indicates something vanishingly rare. The second number is the over/underrecordedness in iNat: A positive number indicates that the species forms a higher proportion of records in iNat than in NBN (i.e. overrecorded), and a negitive number implies that it forms a smaller proportion of iNat records than in NBN (i.e. underrecorded - a species with no iNat observations is '-100%').

To give you an idea of the rarity scale, here are a few other British species with increasing rarity values: Episyrphus balteatus (0,45%), Epistrophe eligans (10,45%), Eupeodes latifasciatus (19,-55%), Volucella inflata (31,-38%), Eriozona syrphoides (40,-64%), Pipiza luteitarsis (49,-86%), Chalcosyrphus eunotus (60,-95%), Blera fallax (77,-100%), Neocnemodon brevidens (90,-100%), Syrphus nitidifrons (100,-100%).

(Unfortunately I have not been able to find a particularly good source of information for the presence/distribution of species on the island of Ireland - so comments on distribution will only cover Great Britain. Note that fewer species are present in Ireland - obviously the commonest species in Britain are the most likely to also be present on the Emerald Isle. My apologies.)

You may want to look through the remainder of species I don't elaborate on for additional species with low rarity and significant underrecordedness, especially if you examine collected specimens - there are some extremely common species almost completely missing from iNat because they require microscopy - e.g. Neoascia podagrica (7,-98%), Syrphus vitripennis (6,-99%), Platycheirus clypeatus (8,-99%), Sphegina clunipes (20,-100%).

Hopefully this will help us improve hoverfly diversity on iNatUK, and be quite fun too!

[Boring bit: I compared iNatUK's hoverfly records for each species with the records for that species on the NBN atlas to determine whether they are under- or overreccorded on iNat. To do this I looked at the proportion of all hoverfly records that represented the species in question: if the species is a greater proportion of all hoverflies on iNat than it is on NBN I call it 'overrecorded', and 'underrecorded' if it is a smaller proportion of all hoverflies on iNat. If a species represents 1% of hoverfly records on NBN but only 0.5% on iNat it is 'underrecorded by 50%', if the same species represented 5% of hoverfly records on iNat it is 'overrecorded by 500%'. Crude, but hopefully that makes some sense.]

[Incidentally, the 22 overrecorded species are: Volucella zonaria (+1034%), Epistrophe melanostoma (+473%), Cheilosia caerulescens (+331%), Volucella inanis (+309%), Myathropa florea (174%), Merodon equestris (+169%), Eristalis similis (+155%), Eristalis tenax (+91%), Volucella pellucens (+78%), Chrysotoxum festivum (+63%), Meliscaeva auricollis (+63%), Eristalis pertinax (+57%), Dasysyrphus albostriatus (53%), Episyrphus balteatus (+45%), Epistrophe eligans (+45%), Eupeodes corollae (+39%), Epistrophella euchroma (+36%), Rhingia rostrata (+32%), Xanthogramma pedissequum (+26%), Sphaerophoria scripta (+25%), Chrysotoxum veralli (+23%) and Scaeva pyrastri (+17%). Most of these make sense as the sort of species citizen scientists like ourselves will most easily notice, others (such as Epistrophe melanostoma) seem to be there more as a quirk of small numbers. Rhingia rostrata and Cheilosia caerulescens may be there because of their recent explosion in numbers - NBN goes back to a time when they were much rarer but most of iNat's data is very recent.]

Posted on January 20, 2024 10:33 PM by matthewvosper matthewvosper | 6 comments | Leave a comment