UK Hoverflies (Syrphidae)'s Journal

July 1, 2024

State of the Syrphs - 1-Jul-2024

So here we are! It was almost exactly a year ago that we made this project active in an attempt to create a team for the curation of iNatUK Hoverflies and to improve the data quality going through to HRS. We now have over 100 members, some have joined for the information, and some - with varying degrees of experience - have become really active participants in the task above. That's all great. Thanks to everyone who has joined, read, participated in, used or enjoyed anything in this group :).

I don't want to make this an annual review though - it is about the transition from June to July as usual. But now all the graphs have 12 months of data so...

    Annotations and the Euro 24 Annotatathon Tour

One of the most immediate impacts of the project was to vastly increase the proportion of observations receiving sex and life stage annotations. Before the project these were less than 20%. Quite a few people got on board with this straight away as something they could do. This is the last time you will see that initial impact in the graph below (I'm only going to keep 13 months of data on these graphs). We maintained our high proportions this month: here are the proportions of new observations that received annotations before the end of the month.

And the total proportion of all UK hoverflies annotated with sex continues to grow, and is now over 75% for the first time:

You can see there the huge impact of the original 'Annotatathon' event back in November. (Please remember that a few hundred old observations have been left deliberately unannotated with life stage because they cause problems for HRS - please do not add life stage annotations to any remaining pre-2022 observations)

As a bit of a side-hustle, during the Euro 24 football tournament it was suggested that we annotate observations during the matches from whichever countries are playing. During the tournament so far I think we've added about 60,000 annotations! I've been posting updates here - the next update will be after the round of 16. For participating European countries outside the UK the proportion of observations with an annotation has increased from 27% to 35% for sex, and from 26% to 43% for life stage. Some smaller countries have been fully completed.

    Observations

5500+ observations were uploaded in June: the most ever in a month. They provisionally included 113 species, matching last month's record. Here are some species to look out for in July.

June's highlights include: Microdon devius, Pelecocera tricincta, Sphegina elegans and S. sibirica, Mallota cimbiciformis, Pipizella viduata, Epistrophe diaphana and a flurry of Myolepta dubia.


(note these are the species uploaded during the month, not necessarily observed during the month)

    Identifications

Incredibly, the increase in the NeedsID pile is again just a few hundred, despite the increase in observations. For two weeks in early June we absolutely smashed any previous record for IDs - nearly 3500 a week! This is testament to those who do a regular bit on new records each day, and some people I notice taking first steps into the world of identifying - all adding up.

35 genera are up, 31 unchanged and 5 down.

If you are interested in helping with identifications, don't feel you need to do it alone - you can always tag in myself or another of the top UK identifiers if you want someone to check what you think. A safe way to get started is to try identifying things that don't yet have a species ID - that way your ID does not make it research grade. Gradually, and with a few mistakes, you will gain confidence. You can find a URL for this task here. Clearly someone has been doing this, because the number stuck above genus has decreased by 5% this month! Well done you :)

Here is the breakdown by tribe, and the deeper dive into Syrphini as usual:

    Obscured Locations

Another thing we have tried to do over the last year is spread the word that using obscured locations for privacy settings causes problems for recording schemes (not just the hoverfly scheme). NBN recommend pinned locations as an alternative. The proportion of obscured locations in June was below 3% for the first time since December (when total numbers were smaller and therefore proportions more random). I don't know the reason for that - whether some people have changed their settings or whether it is random variation.

So finally, thanks to all of you who have engaged with this project in whatever way. I think we've made a difference both to people on iNat, and hopefully also to the recording scheme as they field the iNat data that goes through to them. I want to give a particular shout-out to @rkl who has recently done a great job feeding back whenever HRS have corrected a mistaken ID fed through from iNat.

Happy Syrphing for July!

All data collected on 30th June 2024

Posted on July 1, 2024 12:16 PM by matthewvosper matthewvosper | 2 comments | Leave a comment

June 18, 2024

Euro 24 Annotatathon Tour - Updates

Updated 03-Jul-2024

Hello all,

The first round of group games is over, and it's been quite fun seeing familiar names pop up on observations all over Europe when people are obviously watching the same games! Given that this activity is not core to our purpose as a project - which is for the UK , I don't want to create lots of posts about it (although it gives us all a chance to practice adding annotations - which is a core activity), so I'll just update this post again after each round of group games, the round of 16, and the end of the tournament.

Remember - you don't have to watch the football to join in!

End of first round of group games:

We've added life stage annotations to more than 6% of all non-UK European hoverflies! and sex annotations to 2%, Very cool! (I think it's fair to assume that the jumps are down almost entirely to us!) In particular some of the smaller countries have been greatly affected. I think the biggest total number of annotations added has been to Denmark, while the biggest proportional changes have gone to Serbia (Obviously some of us were watching the England-Serbia match!) You can see the difference in the darker coloured parts of the bars.

End of second round of group games:

Well over 50,000 sex and life stage annotations have been added to European observations since the start of the Euros. I can't say how many are due to us, but it is an increase of 18.5% compared to the number of annotations pre-tournament. And that's for the whole of Europe not just participating countries. Wow. (Participating countries account for 87% of European observations)

4% of all non-UK European hoverflies have received a sex annotation, and 13% have received a life stage annotation.

It may be a little more challenging to choose which country to annotate in this third round of games since matches are being played simultaneously. It looks like Austria, the Netherlands and Poland could particularly do with a little bit of love. Hosts Germany got the biggest numerical increase this time round with nearly 5000 annotations added. Switzerland, France and Belgium also saw nearly or more than 3000. Proportionally, Georgia and Romania did well.

(Note that I've collected these data at the end of each day for the teams that played that day)

End of Group Stage

Since more teams have been playing each day, fewer days in total, and with matches being played simultaneously, it's not surprising that fewer annotations (13500) have been added in the last round of group games. Nevertheless Germany still racked up an impressive 5800+ annotations added. Proportionally, Croatia, Slovakia and Slovenia did the best. Countries needing the most annotations are still Austria, Denmark, France, Germany, Italy, the Netherlands, Poland, Portugal and Spain. Poland are now out of the tournament - though don't let that stop you if you fancy that challenge (I will continue to update all countries). I think I'll update at the end of the round of 16 as well as the end of the tournament.

During the group stage, 7% of non-UK European hoverflies have received a sex annotation, and 15% a life stage annotation.

After Round of 16

We've added more than 15,000 annotations during the round of 16 - for participating countries excluding the UK we've annotated 10% or all observations with sex, and 20% of all observations with life stage, which I think is quite spectacular!

Italy got the most attention this time with nearly 3000 annotations added - which is just as well given they've crashed out! Turkey did the best proportionally. Of the countries remaining in the tournament it's the Netherlands who need the most love (proportionally).

Here are the graphs

Posted on June 18, 2024 10:08 PM by matthewvosper matthewvosper | 0 comments | Leave a comment

June 13, 2024

Euro 24 Annotatathon Tour

Hi all,

With the Euros about to start I did wonder about taking a continental excursion...

Now I don't wish to detract from the good work we are doing with UK hoverflies, but it did occur to me that I'm likely to end up watching a goodly number of matches without necessarily being engrossed by them... and my laptop will be handy. I think I might set about doing some annotating in the countries that are playing - perhaps swapping at half time!

Anyway, feel free to join me. As you can see below, most of Europe is still at the levels of annotation that the UK was before this project got underway. In fact, after the success of November's annotatathon and our subsequent activities, more than half of European hoverflies with life stage annotations are now in the UK! (and just under half of those with sex annotations). There aren't really any additional confusing things for annotations in the rest of Europe compared to the UK, and it's a great opportunity to learn if you are new to this.

Adding annotations is a great way for beginners to see the diversity of hoverflies. It's fairly simple, you can even avoid the few tricky genera completely by sticking to the subfamily Syrphinae. Here's how to do it. (Of course you don't need to be watching the football!).

You can use the links from the Useful URLs post, but just change the country.

Here are the participants in the Euros, showing first the percentage of hoverflies with annotations, and secondly the absolute numbers of annotations compared to the total number of hoverfly observations in each country (in green):

Posted on June 13, 2024 07:59 PM by matthewvosper matthewvosper | 7 comments | Leave a comment

May 31, 2024

State of the Syrphs - 1-Jun-2024

Hello everyone,

Hope you've had some chance to enjoy nature this month, wherever you've been. It's been a great month. We seem to have had a bumper spring for iNat hoverflies, which seems to be improving the diversity of what is recorded compared to previous years.

Fantastically, we have passed 100 members this month. Thanks to everyone who has gotten stuck in and made it feel like a team effort to improve our hoverfly data for the benefit of the national recording scheme. If you are new, please be sure to read this key article about how to make your observations as useful as possible to the national recording schemes (because much of the advice there does not just apply to hoverflies).

    Updates

I have tweaked the URLs in the Useful URLs post. The links for adding sex and life stage annotations now include Research Grade. Originally they didn't because it seemed more important to focus on observations that were yet to go through to HRS, rather than observations that had already gone through. But now that pile is basically done, and we only need to keep up with new observations as they come in, and deal with the old RG ones.

I have also added a new URL, "Pre-Mavericks", which allows you to find the observations where there is a disgreement that is potentially one ID from resolution (depending on which way it needs to go!). It deploys the Pre-maverick project by @jeanphilippeb, which you can also use for other taxa you are interested in.

    Observations

Another record month for observations with just over 4000 posted (the previous record for May being 2854 last year). In terms of diversity, we have provisionally recorded 113 species, more than any previous month! Highlights include: Cheilosia lasiopa, Pocota personata, Brachyopa pilosa, Criorhina asilica, Dasysyrphus venustus s.s., Pipiza luteitarsis, and a smattering of P. austriaca

In June, more species are at their peak than any other month of the year, so have a good one! Here's what to look out for in June.

    A history of the NeedsID Pile

We are approaching the point where we will have a whole year's worth of data from this project. One thing that's bugged me for a while is the inability to compare what we have acheived to previous years when there was no project. You cannot get from iNat how many observations needed ID at a point in the past. Anyhow, one very dull evening I had a crack at estimating the size of the NeedsID pile in times past. Starting from Jan 2018 (before which only 0.5% of observations were posted) I used the number of observations posted and IDs made each month, coupled with the average number of IDs that UK hoverflies have needed to reach Research Grade (which is 2.45 if you're interested!) to estimate the change in the NeedsID pile each month, eventually I reached the recent months for which we have real data and tuned the single unknown constant until they matched (gory details at the end). I think the graph below must be accurate enough to tell a true-ish story - maybe I'll be able to improve it once we have some real data from the upward curve. But see what you make of it, I definitely think we've made a difference!

    Identifications

Despite the record numbers of observations, the NeedsID pile has grown this month by only a few hundred. It looks like we have a really good chance of keeping it well below last year's peak. It's been especially cool to see members of this group stepping up and starting to try a few IDs for other people.

Here's the usual breakdown of the tribes, and the deep dive into Syrphini.

Only 7 genera have decreased, with 21 unchanged and 43 increased. It's nice to see though that the number stuck at higher levels has actually decreased by more than 5%. The biggest climbers (with >50 obs to start with) are, Chrysotoxum (+19%), Eupeodes (+18%), Helophilus (+16%), Rhingia (+16%), Xylota (+16%), Cheilosia (+15%), Melangyna (+15%), Meliscaeva (+13%), Platycheirus (+13%), and Sphaerophoria (+12%). Platycheirus is the runaway train here, leapfrogging Eristalis to become the neediest genus with nearly 1500 observations needing ID. Cheilosia is also rising much from a very high base. Just over 70% of observations posted in May are already Research Grade.

    Annotations

We have maintained a high level of annotation. Great job!

    Obscured locations

Obscured locations remain at about 4.5%. Observations with obscured coordinates cannot be used by the hoverfly recording scheme (and most other recording schemes). For an alternative way to address privacy, recommended by NBN, see here.

Right, that's all! Happy Syrphing for June!

All data compiled on 31st May





[Gory details
The average number of IDs per research grade observation was calculated as the total number of IDs made on RG observations posted before the end of 2023 divided by the total number of such observations. The time limit was intended to keep out more recent observations for which the numbers will still be changing more. Call it A. It turns out that for UK hoverflies A=2.45. (This includes the original poster's ID).
The number of observations needing ID at the start of 2018 was assumed to be as small as possible given the number of IDs and observations before that time, assuming that A=2.45 and all observations had an ID on upload (no unknowns). Any error from those assumptions shouldn't matter because all the numbers are so small at that point. Given these assumptions the maximum possible number of RG observations at the start of 2018 is [ IDs(Pre2018)-Obs(2018) ]/(A-1), where the subtractions account for the observers' initial IDs.
Therefore the starting point, NeedsID(Jan 2018) = Obs(Pre2018) - [ IDs(Pre2018)-Obs(2018) ]/(A-1).
Each month the NeedsID pile changes by Obs(Month) - K.[ IDs(Month)-Obs(Month) ]/(A-1) where K is a fudge factor multiplying the maximum possible number of RG observations from that month (0 < K < 1) to account for the fact that we don't in fact make the maximum possible number of RG observations per ID. This is the number that was scaled to match the true data from recent months. K=0.913, which suggests that on average we make just over 90% of the number of research grade observations possible with the number of IDs we use. This is assumed to have always been constant.

]

Posted on May 31, 2024 10:01 PM by matthewvosper matthewvosper | 0 comments | Leave a comment

May 1, 2024

State of the Syrphs - 1-May-2024

We have lift-off! (bzzzz.....)

It's been quite a month on the hoverfly front. Last month I predicted we might get 2,500-3,000 new uploads in April (the previous record for April being 1,824). We actually had nearly 3,800! Only July and August last year have ever had more. Nearly 1,200 of these were observed during the four days of the City Nature Challenge (CNC). The identification window for the CNC ends on Sunday. More comments on that below.

I'm not going to predict next month! May is an exciting one for species diversity (read all about it on What to look out for: May!). But it will be interesting to see how it compares to the last time there was an early CNC, 2020, when the number of observations in May was actually fewer than in April.

With such numbers it is remarkable how well we have kept up!

Provisionally 78 species were recorded, smashing the previous April record of 60 from 2022. Highlights include Neoascia interrupta, Anasimyia interpuncta, Cheilosia ranunculi and Epistrophella euchroma/Meligramma euchromum

The link to iRecord appears to have got back to normal, so we can go back to normal routine.

Identifications

It is indeed the first month since September that the NeedsID pile has grown - but not by as much as it might have done - up by 12.7%. Only 8 genera decreased (small ones, and not by much), 28 were up and 35 were unchanged. Here's the breakdown by tribe, and the breakdown of Syrphini by genera:

The biggest % climbers (with >50 obs to start with) were: Syrphus (+114%), Melanostoma (+55%), Epistrophe (+41%), Helophilus (+30%), Platycheirus (+24%),Sphaerophoria (+22%), Meliscaeva (+15%), and Eristalis (+13%). In addition to those mentioned last month the following genera also now have >100 observations needing ID: Epistrophe (106), Sphaerophoria (104).

The total proportion of observations that are research grade has fallen slightly to 88%. Just over two thirds of observations uploaded in April are research grade already, including just under half of those posted during CNC.

Annotations

Somehow we managed to maintain an extremely high level of annotation.

Obscured locations

These continue to bobble around the 4-5% mark. If you used obscured locations to preserve privacy or for whatever reason, and you haven't already given thought to using Pinned Locations instead, NBN encourage you to consider it. Observations with obscured locations cannot be used by the Hoverfly Recording Scheme.

Hope you all have a great May!

All data compiled on 30th April

Posted on May 1, 2024 10:58 PM by matthewvosper matthewvosper | 0 comments | Leave a comment

April 18, 2024

Current transfer issues to iRecord, helping HRS - please read.

Hello everyone,

Roger Morris noticed a sharp drop in iNat observations coming through to iRecord in April. Having investigated a bit, this seems to have to do with a technical change in the way iNat is linking to images. This has been interpreted by the bridge as a form of editing of these old observations, and caused a large amount of information traffic between iNat and iRecord that has clogged the system and caused significant delays in the transfer of new observations.

The result is that Roger has received fewer than 1/3 of the observations he should have so far this month, and there is a fair likelihood that a large number of observations are going to be dumped on him all at once at some point in the future - just as things are getting really busy anyway.

I suggest that for the next few months we generally hold back on the following activities to avoid exacerbating the issue: 1) annotating pre-2024 research grade observations. 2) making pre-2024 observations research grade.

Instead we could focus on 1) Annotating and identifying 2024 observations as they come in LINK 2) Annotating observations of any age that are still in the Needs ID pile (only sex annotations required now) LINK 3) Identifying observations of any age that are stuck at subtribe or above to finer levels LINK.

This is more than enough for us to get on with :-)

Posted on April 18, 2024 08:19 AM by matthewvosper matthewvosper | 4 comments | Leave a comment

April 14, 2024

State of the Syrphs - Pre-CNC update and strategising

Hello all,

With the ides of April behind us, and despite the weather, it looks like my estimate of 2500-3000 observations this month will be too low. We are already approaching 1500 and the City Nature Challenge looms! It starts on April 26th. Last year the period of the City Nature Challenge saw more than 1300 hoverfly observations uploaded.

For those not familiar with the City Nature Challenge you can read all about it here. It includes four days of observing (26th-29th) and nearly a week more to upload and identify things. For the purposes of the City Nature Challenge it is important that as many observations as possible are identified by May 5th. You can use this link to identify these observations specifically. If you would like to help this intensive ID effort you might want to familiarise yourself with how to identify some of the top 10 species from last year, which accounted for well over 500 observations:

  1. Epistrophe eligans
  2. Eristalis pertinax
  3. Episyrphus balteatus
  4. Myathropa florea
  5. Melanostoma scalare
  6. Helophilus pendulus
  7. Syrphus ribesii
  8. Platycheirus albimanus
  9. Rhingia campestris
  10. Leucozona lucorum

All the best!

Posted on April 14, 2024 10:10 PM by matthewvosper matthewvosper | 0 comments | Leave a comment

April 1, 2024

State of the Syrphs - 1-Apr-2024

Hello Syrphers!

It has been wet, hasn't it? Just a little bit. Ah well.

What to look out for...

April is lift-off month for hoverflies - check out which hoverflies are at their peak, and which are getting going in this month's 'What to look out for', which contains advice on getting identifiable pictures of the difficult 'black jobs' that form a significant part of the fauna at this time of year. (Bear in mind that species will appear earlier in the south and later in the north).

Keeping up with New Observations

Despite the weather, an awful lot of hoverflies have been uploaded (for March anyway)! This continues the trend of 2024 - so far well over three times as many hoverflies have been uploaded as in any previous year. Some of that is certain users uploading plenty of photos from previous years, but there has also been a significant increase in real time observations, easily more than twice as many as any previous year.

I don't expect that to continue - it is relatively easy to double or treble the small numbers at the start of the year. Nevertheless we have more than kept up with the influx and so the NeedsID pile continues to diminish. 87% of this month's new observations are RG already. Don't forget the handy URLs here which can help us keep up!

What would we need to do to keep up with observation numbers in April? One complicating factor is that this year much more of the City Nature Challenge (CNC) period is in April - so just comparing to last April (when all of the upload period fell in May) won't work. (Last time CNC was mostly in April - 2020 - there were more observations in April than May!) Last year there were nearly 2500 hoverfly uploads from April 1st to the end of the CNC. Based on the increase so far this year it doesn't seem inconceivable that there could be 2500-3000 in April this year. I worked out that on average an observation needs about 1.5 IDs additional IDs to reach RG (i.e. additional to the observer's ID), so that's up to 150 IDs per day on average between all identifiers to keep the pile the same size. In reality they will not be spread evenly - there will be a big surge in the week from Fri 26th. It will be interesting to see if April is the month the NeedsID pile starts to get bigger again...

Identifications

I suggested last month that we try to get the NeedsID pile below 8500 (half of what it peaked at last year). With a bit of a late activity over the weekend we have achieved that!

8 genera have increased (but not by much), with 30 unchanged and 33 down. The biggest fallers (with >50 obs to start with) are Pipiza (-85%), Neoascia (-76%), Eumerus (-66%), Xanthogramma (-65%), Syrphus (-56%), Melanostoma (-54%), Parhelophilus (-49%), Eupeodes (-43%), Epistrophe (-38%), Meliscaeva (-38%), Rhingia (-28%), Platycheirus (-26%), Chrysogaster (20%), Merodon (-20%), and Helophilus (-11%): Those are some serious numbers, so well done for your contributions. The neediest genera now (those with >100 observations) are Eristalis (1176), Platycheirus (1021), Cheilosia (595), Melanostoma (419), Eupeodes (364), Helophilus (198), Chrysotoxum (121), Xylota (113), and Syrphus (108). May I make a personal plea on behalf of Eristalis? It's my favourite genus, but I've already identified everything still needing ID in the UK so I can't do any more, and the numbers haven't moved much since new year. Anyone fancy having a go?

Another thing that is worth noting is that an increasing proportion of the NeedsID pile is not even ID'd to genus - currently 40%. This includes nearly 50% of Syrphini languishing at tribe. Identifying these is a great exercise for beginners because you don't have the pressure of making things research grade. The following rather messy pie chart shows you the whole NeedsID pile divided by genera. (Probably won't be readable on the app - but the big blue block is 'No Genus yet')

And here is how we did it. You can see just how many more IDs have been added over the winter compared to previous years, and it really is impressive :)

Annotations

It's also been a very successful month on the annotations front. Sex annotations over 95% for the first time.

Obscured locations

Unfortunately we had quite a high proportion of obscured locations this month. I wonder if more observation has taken place close to people's homes due to the relatively poor weather. Observations with obscured locations cannot be used by the Hoverfly Recording Scheme. An alternative that avoids this problem is 'Pinned Locations'.

Finally, Happy Easter to you all, and Happy Syrphing for April!

All data compiled on 31-Mar-2024

Posted on April 1, 2024 08:27 AM by matthewvosper matthewvosper | 2 comments | Leave a comment

March 1, 2024

State of the Syrphs - 1-Mar-2024

Hello Everyone!

A happy Spring to you all!

What to look out for:

All of the What to look out for articles are now available on the project journal, including the March edition. This is the month hoverflies just start to pick up. One early riser, Melangyna quadrimaculata is best seen this month, and the article suggests how to give yourself the best chance of seeing it, and photographing it identifiably. There are a few other species getting going too :)

Annotations

A little piece of information I picked up recently, courtesy of @rkl: When a record becomes research grade and is sent to the hoverfly recording scheme subsequent changes made in iNaturalist are still sent through until the record is confirmed in the iRecord system used by HRS. Only once HRS have confirmed the record do changes made in iNat have no further effect. So do not despair if you find a new record that is already research grade but hasn't been annotated! Add the sex and life stage as quick as you can, and you might still be in time. (This includes if the ID is wrong - add a correcting ID and the observation will be withdrawn from iRecord until it becomes research grade again).

Anyway, we've just had our best ever month for keeping up with sex annotations, bravo! Just a smidge short of 90%. And life stage annotations remain very high.

Also, two thirds of all UK hoverfly observations now have a sex annotation.

Identifications

Last month I suggested that we aim to get the total number of observations needing ID down to 8500 (half of last year's peak), and we're not doing too badly towards that. March is really the last month of the off-season (although things are just starting to pick up). With a bit of a push we might just make it!

Remember the handy URLs here that can help you find what you want to identify and annotate, and keep up with new observations.

Here's the usual breakdown of the NeedsID pile by tribe, and deeper dive into the largest tribe, Syrphini. Syrphini is reducing fast, but Melanostomini, Bacchini, Eristalini and Rhingiini remain stubbornly similar in size.

7 genera have increased slightly, 28 are unchanged and 35 have fallen in numbers needing ID. The month's biggest % fallers (that had >50obs to start with) are: Eupeodes (-55%), Xylota (-46%), Xanthogramma (-13%), Chrysogaster (-12%), Helophilus (-12%), Parhelophilus (-12%) and Eristalis (-11%).

If you are new to identifying, a good way to get started is by identifying observations that are stuck at higher levels - bringing down the ID to genus, or species if you know it. This is less pressure than making things research grade. A third of all observations needing ID have not yet been identified to Genus; you can find them using the link on the URLs page

The neediest genera now (those with >100 obs needing ID) are: Platycheirus (1373), Eristalis (1186), Melanostoma (978), Eupeodes (635), Cheilosia (597), Syrphus (249), Helophilus (223), Xylota (120), and Neoascia (105). Hark at that! Eupeodes down to 4th! You may want to consider learning these genera, to make a bigger difference with your effort. The most accessable are probably Eristalis, Melanostoma, Syrphus, Helophilus and Xylota. See the resources page!

Have a great March!

All data compiled on 29-Feb-2024

Posted on March 1, 2024 12:15 AM by matthewvosper matthewvosper | 0 comments | Leave a comment

February 8, 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 8, 2024 10:06 AM by matthewvosper matthewvosper | 0 comments | Leave a comment