Tuesday, 10 April 2018

Southern Bristletail, Dilta hibernica?

Southern Bristletail, Dilta hibernica?

I recently came across a colony of bristletails so I took the opportunity to examine a few, which I tried to key out using:
Delaney, M.J. (1954) Handbooks for the Identification of British Insects. Vol. I, Part 2. Thysanura and Diplura. Royal Entomological Society, London.

It was quite easy to get these to the genus Dilta based on the conformation of the ocelli:
Bristletails - Eyes and ocelli_

Dilta - Ocelli

After that, it got difficult/impossible. In reality, based on the UK distribution this has to be the Southern Bristletail, Dilta hibernica (because it can't be Dilta littoralis in Rutland as this is a marine species), but it's impossible to confirm this as identification of Zygentoma is based on adult male specimens - females and juveniles cannot be identified to species level, but most if not all populations are parthenogenetic (no males!).

None of the specimens I examined were adult males, so I could well be on a loser with this. The reason I would like to record this species rather than just walking away (apart from taxonomic completeness) is because these are relatively large and quite visible arthropods and I'm not the only person who will have seen these. I could just call it "Dilta sp." or "agg.". The alternative would be to list it as Dilta hibernica sensu lato, but in reality, "sp." would be more accurate if less precise.

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