Posted by Sundew on 31-08-2007 18:02
#9
In the internet, there is a paper on syrphids by D. Miller (Transactions and Proceedings of the Royal Society of New Zealand, Vol. 53, 1921;
http://rsnz.natli...03850.html), where the faces are described:
Face of varying shape; concave, convex, arched, or vertical below antennae, with or without a central tubercle or swelling; sometimes produced at oral margin; clothed with hairs or bare, and sometimes transversely wrinkled; oral margin horizontal, descending or ascending...
In a following key, you get to
Melanostoma via
face not vertical to oral margin but with a distinct knob in middle
I could not find a more recent paper explaining the nature of this round knob - sorry! It's just there, fancy
Melanostoma design...
Sundew