Cacopsylla melanoneura

Previously known as Psylla melanoneura but now placed in the genus Cacopsylla.

I have encountered a number of challenges identifying this species, but assuming I'm now getting them right, this is probably the commonest species in the genus, at least here in my garden. I have some hesitation because the majority of specimens I have examined have had clearly green abdomens. The key implies that this should only be the case with teneral individuals, but I'm pretty sure that not all of these are teneral. Neither of the photos of adult melanoneura on the British Bugs website show any hint of green and nor to most of the other photos of melanoneura on the internet. So am I going wrong? If you think I am, please get in touch!

I can't see what else they can be - unless I'm overlooking something, none of the other options seem to fit, and the genitalia and genal cones (useful in identifying psyllids) match melanoneura. The British Bugs website says that affinis can only be separated from melanoneura by male genitalia, and indeed the diagrams in the key for female terminalia of the two species do look very similar indeed. The key does show slight differences in the shape of the genal cones which presumably applies to both sexes if it's reliable. The key differentiates affinis (using its former name Psylla subferruginea) by the wing colour, quite early in the key, but the comment on British Bugs website (and most of the accompanying photos) suggests this is not reliable in all cases. So far all my males have had genitalia and genal cones matching melanoneura and not affinis, but if genal cones alone are not reliable then perhaps the females should be regarded as either melanoneura or affins. Incidentally, affinis isn't meant to have green abdomens either - a few species do, but unless I've gone wrong somewhere, they can all be eliminated on other characters.

Before moving on to the tricky individuals with green abdomens that I keep catching in my garden, here are a couple of more typical (?) individuals that I took elsewhere and identified a while ago.

male Cacopsylla melanoneura showing genal cones and genitalia, Bacton Wood (Norfolk, UK), 14th October 2017

Of all the melanoneura I've recorded this is the darkest. Unfortunately I didn't manage to photogrpah the key characters used to identify it.

female Cacopsylla melanoneura, North Elmham Cathedral Meaodws (Norfolk, UK), 16th March 2020

Out of eight specimens I have just examined, only this one didn't have a green abdomen, and even this lacks the dark purply tones that can be shown by Cacopsylla melanoneura.

female Cacopsylla melanoneura showing forewing and terminalia, North Elmham (Norfolk, UK), 3rd July 2020

These all had green abdomens. I'm still questioning in my head whether these really can be melanoneura, and yet the bits that count all seem to point that way.

male Cacopsylla melanoneura showing forewing, genitalia (before and after clearing) and genal cones, North Elmham (Norfolk, UK), 4th July 2020

female Cacopsylla melanoneura showing forewing, genal cones and terminalia, North Elmham (Norfolk, UK), 4th July 2020

I think I put the tweezers through this one's face, but one genal cone survived...

male Cacopsylla melanoneura showing wings, genal cone and genitalia (before and after clearing), North Elmham (Norfolk, UK), 25th August 2020

male Cacopsylla melanoneura showing forewing and genitalia (before and after clearing), North Elmham (Norfolk, UK), 22nd September 2020

female Cacopsylla melanoneura showing wings, genal cones and terminalia, North Elmham (Norfolk, UK), 16th June 2021

female Cacopsylla melanoneura showing forewing, genal cones and terminalia, North Elmham (Norfolk, UK), 18th June 2022

Although it hadn't been apparent in life, this last one of the batch had the stronger hint of colour-wash across the forewings than the others when I examined it, and perhaps slightly more conspicuous spinules, but I still can't make it anything else. It spent some time spinning rapidly on its head before settling for a traditional photo...

female Cacopsylla melanoneura showing forewing, genal cones and terminalia, North Elmham (Norfolk, UK), 24th July 2022

Most of the above examples were identified at the same time, and along with a selection of other psyllids, which gave me the advantage of being able to compare specimens. I did the next one earlier, and had a few problems, arising from the green abdomen again! At the couplet in the key that describes the colour of the insect - mine was clearly greenish in parts so I went down the route of "General body coloration green, green and yellow (spring and summer specimens), occasionally red and chestnut-brown (autumn specimens)" rather than "General body coloration multicoloured; red and brown and deep plum colour, occasionally almost black..." Understandable perhaps given that it clearly DOES have a green abodomen and lacks any deep plum or black. But this second option goes on to allow for, "occasional young specimens with abdomen green, thorax brick-red with pale longitudinal markings" - and that is, well, pretty close (if pale orangey-brown counts as brick-red). If I'd followed that route I'd have ended up at melanoneura pretty straightforwardly. It was taken from hazel, not hawthorn which melanoneura is supposed to feed on, but there was hawthorn in the immediate vicinity.

Carrying on with the green options I eventually reached a dead-end (mali was closest, but with some problems), and in trying to see where I had gone wrong I looked closely at the wings. The surface spinules on the forewing were clearly less dense alongside the veins, which I had taken to be "spinule-free bands along margin of veins". But on closer inspection these bands along the margin of the veins were not completely spinule-free, albeit the spinules were much less dense, with small patches that were spinule-free. Taking the spinules "completely covering membrane" option I ended up with ambigua which occurs on willow. There was willow fairly close, and although I wasn't wholly convinced the shape of the genal cones and abdomen were exactly right, this seemed the most feasible solution. That was all fine until I examined another psyllid (coincidentally also taken from hazel) which also keyed to ambigua, but which was clearly different! On that there was absolutely no suggestion of spinule-free bands along the margins of the veins whatsoever - in clear contrast to the relatively-spinule-free bands I found on this one. There were other differences too, including the shape of the tip of the proctiger, and it was now clear that my tentative ID of this one as ambigua was incorrect. Re-examining the photos and the key again, I now feel confident that it was in fact the same species as the others featured above that I have identified as Cacopsylla melanoneura.

female Cacopsylla melanoneura showing forewing, genal cones (pre- and post-clearing) and abdomen tip (pre- and post-clearing), North Elmham Cathedral Meadows (Norfolk, UK), 4th June 2021

There were a couple of others that I recorded from home in 2019 which look much like the batch from 2020-2022 that I've just examined:

female Cacopsylla melanoneura showing forewing, terminalia (before and after clearing) and genal cones, North Elmham (Norfolk, UK), 7th June 2019

female Cacopsylla melanoneura, North Elmham (Norfolk, UK), 17th July 2019

male Cacopsylla melanoneura, North Elmham (Norfolk, UK), 3rd September 2019