Here are two more photos of the fly I tentatively identified as Chalcosyrphus sp. The first photo shows the all-black coloration with no trace of either steel blue highlights (seen in C. chalybea) or red abdominal markings (seen in C. piger). It also gives a better view of the enlarged and ventrally spinose metafemora. The second photo shows the holoptic (contiguous) eyes that make me think this is a male individual (if, indeed, this is true for syrphids as with tabanids).
I’m hoping that posting these will provide any passing dipterists with the information needed for a firmer ID (and possibly an explanation of the purpose of those intriguingly modified hind legs).
Copyright © Ted C. MacRae 2012