Psammotettix alienus

At last the mystery of my records apparently conforming to Psammotettix striatus (on the surface of it an unlikely identification) is at least partly cleared up. I am yet to find a proper paper clarifying the situation (not sure if one has been published?) but from anecdotes in various places (e.g. Twitter) I think I have an idea what's going on - though if you can confirm or contradict please get in touch. The long and the short of it is:

• Using the old RES key (and Mike Hackston's modernised version), my specimens key to striatus, albeit imperfectly as, for example, most have dark tarsi. The vertex length and, in the case of the males, the genitalia, appear to match striatus best (again, not always perfectly but best).
• According to the RES key Psammotettix striatus is rare and only found in the Suffolk Brecks. Another source implies there is (or was) only a single UK record, from Suffolk (I'm not sure if it's that record that the RES key's description of range is based on).
• The German books don't include striatus, but they do include alienus and using the German references my specimens appear to be spot on for alienus.
• A record of Psammotettix alienus in Cambridgeshire was posted on social media in 2014 as the first for Britain, howevever in 2020 it was clarified that in fact it wasn't new for Britain as alienus is synonymous with striatus. This was later further clarified saying that in fact they are different species, but that previous records of striatus were misidentified alienus, so only alienus is British.
• The 2014 annoucement about the Cambridgeshire record commented that the species is widespread on the Continent and included the hashtag #climatechange implying that it may be a recent colonist. I have no information on its current status, but that at least leaves open the possibility that it could have become common and widespread.
• Last time I looked at the NBN Atlas it still had an entry for Psammotettix striatus, but checking this again now (November 2023) I see that this has now been updated to Psammotettix alienus, with striatus showing as a synonym.

Things I remain unclear about are: 1) is the published description of striatus (as used in the RES and Hackston keys) considered to be accurate for alienus (and if so should I be worried that several of mine have dark tarsi, for example)? and 2) how do you tell the real striatus apart from alienus, assuming they really are two different species.

So it now seems to me that my earlier records which I had tentatively labelled Psammotettix striatus were in fact Psammotettix alienus. I have now recorded further males which also conform to alienus genitalically, although these show some variation in external appearance.

I think the genitalia confirm both of these as alienus. I had initially suspected that they might be two different species as there were a few differences between them: the first had much darker tarsi (only slightly darker than the tibia on the second), an almost entirely dark abdomen (the second had yellow apical sternites but it was otherwise black like the first) and was smaller (about 4.0mm vs 4.2mm for the second). Both had the shorter vertex meaning they keyed to "striatus" and I can only see minor differences in the genitalia, so my presumption is that these differences are within normal variation for alienus. Here is the first:

male Psammotettix alienus showing dorsal view of head/pronotum, face, tip of abdomen from below, tarsi and aedeagus (3 views), Wendling Beck Environment Project (Norfolk, UK), 6th September 2023

Here is the second. The tip of the aedagus was perhaps slightly less indented compared to the first. This is quite hard to see as it is quite membranous and transparent at the tip (the sclerotised region is much more obviously divided at the tip below the actual tip).

male Psammotettix alienus showing dorsal view of head/pronotum, face, tip of abdomen from below, tarsi and aedeagus (2 views), Wendling Beck Environment Project (Norfolk, UK), 6th September 2023

This female looks quite distinctive with its dark and pale pattern, but that didn't really help with the ID process - in fact it might be a problem. It seemed to key fairly straightforwardly to "striatus" until the final couplet - I tried several times in case I'd made a mistake and couldn't see anywhere I might have gone wrong - except at the final couplet where there are a couple of niggles. The hind tarsi are dark (the whole leg is a little on the dark side) whereas the key says of "striatus", "posterior tarsi usually pale." Well "usually" implies not always, so I guess that's not a barrier, but perhaps more concerning is the overall dark and pale pattern. The key describes "striatus" forewing cells as being "hyaline, some narrowly darker edged" which doesn't really tally. The overall length of the leafhopper (front of head to tip of wings) is about 4.2mm and the ratio of length of vertex to that of pronotum is 0.75, both clearly within range for "striatus" and wrong for the alternatives at this couplet. So for now this seems to be a strongly-pigmented "striatus" (i.e. alienus), but identified somewhat tentatively. Please get in touch if you can help resolve it.

apparent female Psammotettix alienus, Wendling Beck Environment Project (Norfolk, UK), 29th October 2022

The next one found nearby the following day on arable land looks very similar, if not quite so contrastingly dark and pale. It keys exactly the same way (including with the same problems at the end) and the measurements are identical.

apparent female Psammotettix alienus, Wendling Beck Environment Project (Norfolk, UK), 30th October 2022

This one also keyed to "striatus" and being a male, I checked the genitalia. The view from behind looks right, though the view from the side isn't quite so slam dunk a match for the figure in the key. Since seeing that Mike Hackston has covered these in his keys I've checked there too, and again the side view isn't quite perfect, being broader at the tip than shown there. However, having now reviewed this against the German books I think it's fine for what we now know as alienus.

male Psammotettix alienus showing aedeagus, North Elmham (Norfolk, UK), 25th July 2019

This species, assuming I am now identifying them correctly, seems to be quite common now - one of the commonest leafhoppers that are coming to light in my surveys in arable/grassland habitat.

male Psammotettix alienus showing head & pronotum from above, rear abdomen from below and aedeagus (2 angles), Wendling Beck Environment Project (Norfolk, UK), 8th September 2023

On this occasion I had 14 of these come to LED lights on a sheet in the middle of an arable field. The length of the vertex was less than 0.8x the length of the pronotum in every case, often less than 0.7x. These are the 5 males - they averaged a bit smaller than the females and 3-4 were very slightly under 4 mm. The genitalia of all 5 matched alienus. In the photos below the close-ups and genitalia photos always follow the photo(s) of the same insect taken while alive.

5x male Psammotettix alienus each showing head & pronotum from above, rear abdomen from below and aedeagus (2 angles), Wendling Beck Environment Project (Norfolk, UK), 25th September 2023

These are the 9 females. They were identified primarily on vertex to pronotum length ratio, but size was also an indicator with all but one being over 4mm (the exception was only a whisker under). As with the males above, in the photos below the close-ups always follow the photo(s) of the same insect taken while alive.

9x female Psammotettix alienus each showing head & pronotum from above, Wendling Beck Environment Project (Norfolk, UK), 25th September 2023