Eurybrachidae (especially the genus Platybrachys) identification in Australia

Across southeastern Australia, brown planthopper nymphs with two distinct 'tails' are a pretty common sighting, and are often seen racing up and down eucalypt trunks. These generally look something like this:

In a large number of cases, these nymphs get identified on iNat (and elsewhere) as genus Platybrachys, or as the species Platybrachys decemmacula ('Green-face Gum Hopper'). However, this is one of the classic citizen science feedback loops! You start off with one person overconfidently identifying something to species; the next person comes along and sees that ID and copies it; then soon enough you have hundreds, or even thousands, of IDs all snowballing off each other. And in the case of iNat, this is even more impactful given this all feeds into the Computer Vision too, and so the problem becomes even more self-reinforcing until the chain is broken.

Yesterday I contacted Murray Fletcher, an Australian hopper authority (and author of these great keys: https://idtools.dpi.nsw.gov.au/keys/auch/index.html), and he put me in touch with Jerôme Constant, a Belgian researcher who is an authority in Eurybrachidae and other fulgoroid hoppers (see his works here: https://www.researchgate.net/profile/Jerome-Constant). Jerôme has been revising many eurybrachids (see a great summary of this as of 3 years ago by @matthew_connors here: https://www.inaturalist.org/observations/27731797 - although more papers have been published since, available at my previous link). My question to Jerôme was:

I see images of eurybrachid nymphs like the one below consistently identified as Platybrachys decemmacula, or at very least as genus Platybrachys. Am I correct in saying that these actually cannot be identified to species, or even genus, from these nymphs, and the best possible ID is to family?

And Jerôme's response was:

"Indeed, it is extremely tricky to ID Eurybrachid nymphs from photos. i am aware of that problem of everyone identifying so many photos (adults and nymphs) as "Platybrachys decemmacula", with little, if any support.
Adults in the genus Platybrachys require male genitalia characters check to ID the species, and this is still awaiting a complete revision of the genus, which is a very complicated one. I already removed a number of species from Platybrachys (Chewobrachys, Fletcherobrachys, Kamabrachys - see my papers available here: ResearchGate) but it is far from finished... so, except for very few exceptions, like Hackerobrachys viridiventris or Olonia nobilis if the photos are from Lizard Island, all should remain on the conservative side of an ID to family level for nymphs (except for Gelastopsis nymphs that show the black markings on frons), and to genus level for adults.
All the rest is speculation."

So the key takeaway here:
all should remain on the conservative side of an ID to family level for nymphs (except for Gelastopsis nymphs that show the black markings on frons), and to genus level for adults.

There is also some more useful info at Murray's Platybrachys page (https://idtools.dpi.nsw.gov.au/keys/fulgor/eurybrachidae/platybra.htm).

As I type this, there are 3,158 observations of Eurybrachidae in Australia, including 712 currently identified as Platybrachys decemmacula. Overall, 931 of the 3,158 are currently identified to species, about 29%: which to be honest is not as high as I thought it would be, so props to people for being conservative with their IDs!

Today I'll be going through these and first of all pushing all nymph observations back to family where required. For observations of adults currently identified to a species level within Platybrachys, I will also be pushing many of them back to either genus if I'm confident, or back to family if it's unclear whether they're actually in one of the other recently split-out genera. I won't be touching anything identified as any of the other eurybrachid genera for now (unless the photos are of nymphs).

Another important thing to note is that, based on current physical specimens, Platybrachys decemmacula has a distribution along the east coast from SE QLD down to around Sydney. Compare that to current iNat records which are from SW WA, across to Adelaide, and then around the entire coast all the way up to Cape York. Although of course it is very possible (and in fact highly probable) that there are iNat records that expand the species' range outside specimens, I highly highly doubt its range is this tremendously wide vs specimens.

When Jerôme finishes revising Platybrachys, perhaps some species will be identifiable from images without genitalia, in which case I will return to these records to re-check them.

As usual, tagging top observers and IDers of this group in this region, as well as interested parties, and feel free to tag anyone I may have missed, or to share this!
@matthew_connors @nicklambert @possumpete @wcornwell @cesdamess @ellurasanctuary @edie42 @julien357 @panyan @pmmridge @reiner @russ87 @cynthia_c @dustaway @coddiwompler @gregrossington @silversea_starsong @psyllidhipster @wongun @bettong-whisperer @greyone @douch @lehelind @stickgrub @ray_robinson @twan3253 @wellsii @debtaylor142 @urliup-wildlife-sanctuary @francytee @glendawalter @juliegraham173 @suelee @jb2602 @dianadavey @imcmaster @donnamareetomkinson @marietarrant @hatwise @alonelycryptid @f_martoni @nomolosx @natashataylor @vireyajacquard @cinclosoma @martin487 @tjeales @gregtasney @steve_hancock @sofiazed1 @scottwgavins @sjmurray55 @gedtranter

Posted on August 22, 2024 07:02 AM by thebeachcomber