Dryops ernesti

My first Dryops, found in a pitfall trap. I didn't find it easy to identify, although I my next ones were much easier after this experience. I started off using Duff and went wrong at the first Dryops couplet. Admittedly the elytral punctures were obvious enough when looking under the microscope, but for ernesti (and nitidulus) they're meant to be easily seen at low magnifcation (20x). Well through my 40x hand lens they were visible, but hardly obvious, so I tentatively took the wrong option. Differences in male and female genitalia are important for most of the other Dryops, so I attempted to remove the abdomen in order to check the genitalia. It didn't break off at the base easily but instead broke part way along and in doing so damaged the genitalia (which on females are unusually large and seem to occupy most of the abdomen). But all was not lost - it was broken at the sideline but the bursa copulatrix was largely intact, albeit detached from the ovipositor.

Comparing the bursa copulatrix with the diagrams in Duff, ernesti looked closest but not immediately convincing, especially as I had already bypassed this in the key. It had a single signa at the end close to the spermathecal duct and 3 rows of tiny hair-like signa in a lightly sclerotised area in what Duff calls region IV. Duff's diagram for ernesti shows a signa close to the end (but just in from the end) and two rows of hair-like signa. Continuing through the key (having passed ernisti) I reached anglicanus. The description for the genitalia fitted, but the diagram showed some additional signa that were absent on mine.

I clearly needed to re-run it through the keys (I'd only had a cursory look at Mike Hackston's key at this point) but it was late and I needed to take a break. By coincidence this weekend I bumped into Martin Collier and mentioned this beetle to him. He mentioned the long perpendicular black hairs of exilis and after this chat I felt that it was most likely that it would probably prove to be exilis and not anglicanus. Going back through both keys (Duff and Hackston) and reading the accompanying descriptions more carefully I was satisfied that it was indeed exilis.

One other thing worth mentioning (?) is the antennae. The antennae of Dryopidae are highly unusual with the enlarged second segment, but they weren't easy to see when the beetle was alive and on death they were retracted so tightly into the head that they were inacessible. Mike Hackston's key uses the number of segments but I found this impossible to determine. I was unable to extract the antennae from their grooves without destroying them and the rest of the head. Maybe it would be easier when freshly dead, or I guess if I'd macerated the head in KOH that might have enabled me to extract them...?

female Dryops ernesti showing genitalia including close-ups of the bursa copulatrix at two different focuses, North Elmham (Norfolk, UK), 15th or 16th April 2022

The next one was easier, though I should have used some fresh KOH to clear the abdomen as the genitalia didn't come out very cleanly and that made it a bit of a job to see the necessary detail. This one was caught in my moth trap.

female Dryops ernesti showing genitalia, North Elmham (Norfolk, UK), 13th May 2022

These two males were also caught in my moth trap. At first I was a bit worried by the shape of the aedeaguses - Duff illustrates this in side view as being straighter than some of the other species but these were considerably more curved. I struggled to get them to lie flat long enough to see them (or photograph them) properly but eventually I got a good enough look at them flat to see that they did in fact fit ernesti.

male Dryops ernesti showing genitalia, North Elmham (Norfolk, UK), 10th May 2023

male Dryops ernesti showing genitalia, North Elmham (Norfolk, UK), 14th May 2023