Towards the end of July last year I found a lot of flies skating on the water surface up on Birsay Moor. I took some field photos and IA kindly identified them as most probably of the genus Hydrophorus, members of the Dolichopidae family. IA also pointed me towards the 1978 Royal Entomological Society key to the family which is freely available online. A quick look at the NBN, OWIARC and the key suggested that Hydrophorus praecox was the likely contender of just a few members of this genus. I went back up on the moor to take some specimens with the hope of obtaining a specific identification. Collected, labelled and put safe in the specimen fridge to await identification. Somehow I managed to lose the specimens in my fridge, however, whilst sorting through some Ichneumons in there the other day they came to light, having been misplaced. Under the microscope and referring to the key it quickly became apparent that the flies were not Hydrophorus praecox which has no wing clouds, my flies have two. Males and females key separately, but the wing clouds eliminated all but three species quite quickly. It then became a bit of a wrestle. I went back to the key and started from scratch, keying out the genus, as IA hadn't been 100%. However, he had been right, the flies were Hydrophorus. I tried Steven Falk's Flickr collection, no Dolichopidae, but, as luck would have it there were photos on Bioimages, Malcolm Storey's fabulous photo resource. These wonderfully detailed photos showed exactly what I was seeing with my specimens and assuaged my doubts with a couplet in the key. Hydrophorus bipunctatus, which is new for Orkney. Photos below include an original field photo and studio specimen images. I've been playing with that Pixel 7 again, it can take images down the microscope quite effectively.
Hydrophorus bipunctatus, original field image, 28/07/2023.
.
No comments:
Post a Comment