Along the Air Line Trail - Stan Malcolm Photos

Following is a transcription of a "conversation" on the "Friends of Coleoptera" Facebook group page, starting with my question about the odd case of finding a beetle larva active atop snow in the middle of winter. The mystery seems resolved, thanks to contributions from entomologists in the Czech Republic, Austria, Mississippi, and somewhere in Central or South America. What a lovely, connected world of beetle people. Friends of Coleoptera is hosted by curator Max Barclay at the Natural History Museum, London - formerly the British Museum of Natural History. (Too bad the rest of the world isn't so collaborative.)

Stan Malcolm Active atop snow at nearly 50 degrees fahrenheit on rail trail that passes through a frozen marsh; Hebron, Connecticut, USA - 15 February, 2013. Tell me this is NOT a Dyticid larva? Carabidae? Or...? Locality pictured. Plenty of other things out (stonefly adults, a chrysomelid adult, a tipulid, and a spider). Was hoping for Boreids for Richard Brown but no luck today.

Martin Fikáček Hi Stan, it is a dytiscid larva. For sure. In Europe I would guess something like Agabus, but I would not guess in case of the USA.

Stan Malcolm Thanks, Martin. I couldn't believe my eyes when I saw it. Ever heard of them active on snow?

Carlos Aguilar Julio I think it is Elmidae larvae, but I'm no very surely!

Carlos Aguilar Julio Now I am thinking it is Dytiscidae !!

Stan Malcolm Martin and Carlos, my surprise was in part because I assumed all the aquatic insects at this time of year would be under the ice, under the water, and burrowed down in the bottom mud. The ice on the marsh is quite thick, as is the snow on the trail. (We had 30 inches of snow a week ago.) The nearest open water was at a beaver dam roughly 100 feet away.

Harald Schillhammer Just showed it to my wife (H. Shaverdo) who is a specialist for dytiscid larvae. She says it is either Agabus or Ilybius. The distinguishing characters can not be exactly seen on the images.

Stan Malcolm Thank you Harald (and your wife). What structures would help your wife to distiunguish between the genera? Perhaps I have a close up view in another photo. Has she ever heard of a larva leaving the water, especially onto snowy ground in winter?

Harald Schillhammer She told me, that it would be helpful to have a sharp and detailed view of the postocular region - something like the head shot but with the postocular region in focus. There should be some bristles which are characteristic for either Agabus or Ilybius. Rhantus can be ruled out because their larvae do not hibernate. I will ask her if she is familiar with such a weird phenology. Maybe I will also ask her to join the group so that she can comment herself - she is only very busy right now preparing a talk on her big project dealing with New Guinean Dytscids.

Stan Malcolm Dytiscid on snow: Harald, this is the best I can do for showing the post ocular area.

Richard Lee Brown I think the comments have missed the point of Stan's posting. The identity is less important than why a dytiscid larva is crawling around on the snow 100 feet away from water.

Stan Malcolm Yes and no, Richard. I'm certainly curious to have an ID, but perhaps a bit more curious about what it was doing out in the winter. To be specific though, the larva was about 100 feet from open water; it was on water (snow), and less than 10 feet from the edge of the marsh ice. In the habitus photo I posted (above), it would have been just to the left of the trampled down path. Kicking myself for not collecting it now, but at the time I couldn't quite believe I was seeing a dytiscid.

Harald Schillhammer FOA - everything (incl. the new head shot) points towards Ilybius. O.k., here's the theory: What I wrote above was not exactly correct. the various stages (eggs, larvae, adults) of Agabus (incl. Platambus) may be found overlapping all the year round. Ilybius, however, seems to have rather strict cycles. The larvae hibernate and when it gets warmer they pupate in spring in the soil in the vicinity of the water bodies where they lived as larvae. I take it from the opening post that this was a sunny day and warm enough also for other insects to become active. So maybe the larva has been fooled , and 100 ft. from the water is not too far. I hope this explains it.

Stan Malcolm Certainly sounds plausible, Harald. Thanks so much for going the extra mile on this. It's a good piece of detective work which I'll share with my UConn colleagues at tomorrow's Lab meeting - with attributions.