So, this garden Stenus from last April had me going round the houses a bit. I found it by suction sampling a patch of lawn which was more moss than grass and it was with two other species of Stenus.
Looking at the key to subgenus, there were no distinct raised margins to the abdomen which took me to a couplet about whether the fourth segment of the hind tarsus was strongly bilobed.
I thought it looked pretty bilobed, so off I went to subgenus Hypnostenus where I got confused. But if I assume it’s only slightly bilobed then it keys to subgenus Tesnus and straight to S. brunnipes and the aedeagus backs that up. The other features of raised head between the eyes and brown legs fit too.
So I guess there is a lesson here somewhere about the variation in bilobedness of tarsal segments but I'm not sure what it is yet...😆
Hang on a mo! Surely this should key differently in the second couplet. I'd go with hind tarsus being "not, or only slightly longer than length of hind tibia". I've just done a batch of Stenus, my Hemistenus all have pretty damn gangly-looking hind tarsi.
ReplyDeleteYeah, coz the 1st segment isn't distinctly longer than the 5th. I think you need to run it again buddy.
ReplyDeleteWhich key are you using? Lott and Anderson? Couplet #1 asks about the abdominal ridges (there are none on this fella) which takes you to couplet 5, which is to the extent of bilobed-ness. Tarsal-tibia comparison is important for sg. Stenus, Hemistenus and Metastenus.
ReplyDeleteDoes that make sense or have I royally f**ked up (again!)
AAAAAAHHHH.....I missed the fact that yours lacked the raised ridges, so took it my 'usual Stenus route' of Couplet 1 >>2 then what I thought should have >>3 but thought you'd gone >>4. Add to that the fact I read your Hypostenus as my Hemistenus and Bob's yer uncle I'm an idiot :D Sorry for the confusion buddy.
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