Sea Bristletail Pterobius maritimus

I found this, my first bristletail, by the moth trap at a holiday cottage about a mile from the sea. I used the old RES Handbook to identify it but found most of the features impossible to see. Eventually I found that by clearing the specimen in potassium hydroxide solution I could make out enough of the characters to satisfy myself, albeit not entirely confidently, that it was Pterobius brevistylis. Some years later I viewed the Tanyptera Project talk about lesser known invertebrates by Paul Richards and there it was pointed out that figures 4 and 11 in the RES Handbook are miscaptioned. I reviewed my photos with this in mind and concluded that as I could not make out the lobes of the eighth abdominal segment it must be maritimus. The text of the key is correct, but I suspect I based my original ID on the diagrams more than the text, not realising that they were the wromg way round. I have to say that this detail isn't perfectly clear in my photos, so I think there might be a case for arguing that this is not a rock-solid identification. As far as I understand it maritimus is much the commoner of the two species.

male Sea Bristletail Petrobius maritimus shwowing head from above and abdomen from below (2 views), Tresidder (Cornwall, UK), 7th October 2020

Holidaying in Cornwall again in 2026 I was pleased to find three more bristletails. One didn't allow me to catch it, and unfortunately the two that I did retain proved to be females. So far as I know, female Pterobius cannot be identified to species. Again I found it impossible to see most of the characters used in the key on the dried specimens, so had to macerate them in potassium hydroxide to make any progress at all. Perhaps if I had put the specimens in alcohol or ethanol on capture this would have been easier? I'm not convinced I could make out the ocelli at all, either before, during or after clearing, but I understand these are in front of the compound eyes not (as you might expect based on many other insect orders) behind the compound eyes. On the cleared specimens I could make out what I took to be the double pairs of coxal vesicles. The antennae seemed a little on the short side for the description of Pterobius, but only marginally so - perhaps they are shorter in females?

I'm guessing these were most likely maritimus, but as females cannot be safely identified (so far as I know) I am only putting them down as Pterobius sp. The first was on the wall of the cottage which was only a few metres from the beach.

female Petrobius sp. shwowing underside of cleared abdomen, Porthgwarra (Cornwall, UK), 11th October 2026

The second was by the moth trap on the sheet the trap had been placed on.

female Petrobius sp. shwowing underside of cleared abdomen and eyes (2 views), Porthgwarra (Cornwall, UK), 15th October 2026