Thread subject: Diptera.info :: Dolichopodidae USA 2011-VI-6 (= Gymnopternus cf. opacus)
Posted by John Carr on 07-06-2011 02:43
#1
Massachusetts, USA June 6 2011, on a leaf. 3 mm long.
I got different results with the keys from Robison and Vockeroth 1981 (MND) and Bickel 2009 (MCAD). Does the lack of strong bristles on the fore tibiae rule out Dolichopodinae? There is a comb of short hairs.
Click pictures for larger size on Flickr.
Front tibia has a comb but no long hairs (
photo)
Edited by John Carr on 03-12-2011 20:41
Posted by Stefan Naglis on 07-06-2011 07:15
#2
Hercsotomus or
Gymnopternus
Posted by John Carr on 07-06-2011 11:44
#3
The key says
Gymnopternus has hairs near the posterior spiracle. I don't see hairs but I'm not sure where the posterior spiracle is on this fly.
Posted by Stefan Naglis on 07-06-2011 15:39
#4
If the pleura ist bare in front of the posterior spiracle, it is
Hercostomus.
Posted by Marc Pollet on 18-06-2011 09:18
#5
It's definitely
Gymnopternus, considering the structure of the hypopygium (also the shape of the cercus), and the parallel course of veins R4+5 and M1+2. The "clutch" of setae in front of the posterior spiracle are sometimes very hard to observe and sometimes only encompass three or four setae, but I am 100% sure that you'll find them eventually in this species.
Cheers,
Marc
Dr Marc Pollet
mpollet.doli@gmail.com
Posted by John Carr on 02-12-2011 02:01
#6
I'm trying to run this through a regional key and I have a really basic question: what are the "hypopygial lamellae"? I only know terminology for Nematocera, and that term is not used. If I am in the right couplet they could be "opaque brown or black, not long-triangular" or "mostly pale or translucent, if brownish then elongate and triangular."
Posted by Igor Grichanov on 02-12-2011 09:44
#7
"hypopygial lamellae" in old keys = cerci
Posted by John Carr on 03-12-2011 02:26
#8
Thank you. Now I can call this fly unidentifiable due to my failure or a bad key, rather than due to my ignorance. The key to
Gymnopternus works for me about as well as the key to North American
Platypalpus, which is to say not at all.
Posted by Stefan Naglis on 03-12-2011 15:02
#9
Hello John, which key have you used?
Posted by John Carr on 03-12-2011 15:34
#10
I am using
Robinson, H. 1964. A synopsis of the Dolichopodidae of the southeastern United States and adjacent regions. Miscellaneous publications of the Entomological Society of America 4:103-192.
Mine resembles
G. frequens Loew but differs in color characters that are considered of specific importance and the shape of the cerci is not quite right.
Posted by Stefan Naglis on 03-12-2011 18:43
#11
Hello John,
Robinson’s 1964 key includes not all North American species. When I use the key, I end at
Gymnopternus opacus Loew. In couplet 28, I regard the hypopygial lamellae as more pale than brown or black.
Best wishes,
Stefan
Posted by John Carr on 03-12-2011 20:38
#12
There are a few cases, like that one, where the language makes more sense to an expert. Also when parts are described as long or short or large or small.
I live in the region covered by Robinson's key.
I figured a Loew species was likely and looked at that couplet, but assumed "hypopygial lamellae small, without a basal lobe or prominent setae" excluded my fly. I would have said they were large and with prominent setae, and shaped a bit differently from Robinson's figure 97. The
photo of the type at MCZ does not show them. It does show almost uniformly pale antennae. Do antennae turn pale after 150 years?