Thread subject: Diptera.info :: Large abdomen (with eggs perhaps?) and green halteres

Posted by Stephen on 30-08-2007 21:12
#1
Can someone provide an ID for this nice fly?

Date: 13 July 2007
Location: Mountains, alongside a small river, West Virginia USA
Edited by Stephen on 30-08-2007 21:37

Posted by Stephen on 30-08-2007 21:14
#2
Here's a view of the front of the head.

Posted by Stephen on 30-08-2007 21:17
#3
Here's the third and final photo.

Posted by Sundew on 31-08-2007 01:17
#4
This is a "pregnant" female, and if the photos were taken in Germany, I would suggest Melanostoma scalare - no idea whether you have the same species in West Virginia. For comparison, look at the pictures given in http://www.natur-...-262.html#.
I hope my amateur opinion is not too far away from truth...
Best wishes, Sundew

Posted by Susan R Walter on 31-08-2007 08:47
#5
Definitely M scalare (unless you have some exact lookalike over there). I find only the females of scalare have those acid green halteres, but also the pattern of abdominal spots and facial dusting indicate scalare.

Posted by Stephen on 31-08-2007 10:06
#6
Sundew, Susan, thanks very much for your help with this one! Your ID sent me to the site www.nearctica.com, and it lists six Melanostoma spp. for the Nearctic, and they are:

Melanostoma ambigua Fallen 1817 (Scaeva)
Melanostoma angustatum Williston 1887 (Melanostoma)
Melanostoma bicruciata Bigot 1884 (Melanostoma)
Melanostoma dubia Zetterstedt 1838 (Scaeva)
Melanostoma mellina Linnaeus 1758 (Musca)
Melanostoma parva Williston 1882 (Cheilosia)

At www.bugguide.net I found a similar gravid female photos identified by Gerard as Melanostoma mellina (acid green halteres too):

http://bugguide.n...760/bgpage

I don't know if mine is the same species as in the BugGuide photo. At any rate I am very glad to know the genus of this one. Thanks again, Sundew and Susan!
Edited by Stephen on 31-08-2007 10:08

Posted by Susan R Walter on 31-08-2007 12:33
#7
Well, now I'm confused - I'll go off and look at some books. :(

Posted by Stephen on 31-08-2007 16:58
#8
Another question I meant to ask before, what is that large round black structure below the antennae?

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

Posted by Stephen on 01-09-2007 13:22
#10
Thanks for the info on that unusual facial structure. Maybe someday we will learn a function that it performs!

Posted by Juergen Peters on 05-09-2007 01:56
#11
Hello!

Up to this thread I never noticed green halteres in Melanostoma. Many of them around here (Ostwestfalen/Germany) at the moment, and I assumed them to be mostly M. mellinum. But yesterday I found this female - with light green halteres! :)
Edited by Juergen Peters on 05-09-2007 18:01