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View Thread :: Family forums :: Syrphidae
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#1 Print Post
Posted on 24-11-2004 16:06

Location: 06 FRANCE
Posts: 32
Joined: 27.10.04

I think this sirphidae is Cheilosa pictipennis, can you confirm my idea.
I see it on september.
Menno Reemer
#2 Print Post
Posted on 24-11-2004 16:26

Posts: 342
Joined: 10.06.04

This is a female of Scaeva selenitica without the characteristic white abdominal markings. This abberation is often called var. unicolor, and it occurs in females in which the ovaries have not developed properly (possibly because of certain parasites).
The specimen is recognizable as a Scaeva species by the swollen frons and the S-curved wing vein r4+5. Cheilosia species do not usually have a yellow scutellum and face.
Paul Beuk
#3 Print Post
Posted on 24-11-2004 16:38
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Location: Netherlands
Posts: 18837
Joined: 11.05.04

I agree with Menno that it appears to be selenitica, but officially the form name unicolor is described for S. pyrastri and treated as synonym for that species.

Females with ovaries have been described for many more species and no doubt the phenomenon will occur in selenitica as well. In some of those species these 'females' are considered to be intersexes because they have intermediate characters between males and females and no developed genital structures. The intermediacy is especially clear in species of Platycheirus and Pyrophaena. In other species it usually appears as if the frons is narrower than in ordinary females.
In your specimen the frons does not really seems to be narrower, and since vague markings are visible (though much darker than normal) I am not yet convinced that this is a true 'unicolor'-like specimen.

For 'unicolor's also see images linked on http://www.bioima...R38418.HTM.

- - - -

Paul Beuk on
Steve Crellin
#4 Print Post
Posted on 24-11-2004 17:31

Location: Isle of Man
Posts: 41
Joined: 01.09.04

I don't doubt that the i.d of S. selentica is correct, baring in mind who has provided it, but what is it about this specimen that says "selentica" as opposed to "pyrastri"?

Generally, I would be relying on the differences in the abdominal markings between the two species, but in the case of this specimen these markings are not really available. Its always useful to know of other characters to use.
Edited by Steve Crellin on 24-11-2004 17:33
Steve Crellin
Isle of Man
Menno Reemer
#5 Print Post
Posted on 24-11-2004 17:49

Posts: 342
Joined: 10.06.04

Oops, I accidentily wrote 'selenitica', but of course I meant pyrastri! Sorry for this mistake. There are two old papers by Van Doesburg which deal with this 'var. unicolor' , and he found several specimens of this abberation with incompletely developed ovaries. I do not have the references of these papers here, but I will let you know later.
Paul Beuk
#6 Print Post
Posted on 24-11-2004 22:38
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Location: Netherlands
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The references:

Doesburg Sr., P.H. van, 1964. Bijdrage tot de kennis van het melanisme bij Syrphiden. ? Entomologische Berichten, Amsterdam 24(6): 117-118.
Doesburg Sr., P.H. van, 1970. Female Syrphid flies without ovarium. ? Entomologische Berichten, Amsterdam 30(8): 157-158.

And about the identity: I was serious about the species more reminding me of S. selenitica than of S. pyrastri, especially the shape of the (very indistinct) markings. I do not have all the details on other characters here, but if someone has the decider why it cannot be S. selenitica, I would be happy to hear.

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Paul Beuk on
Gerard Pennards
#7 Print Post
Posted on 04-12-2004 13:37
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Location: Amersfoort
Posts: 1909
Joined: 07.06.04

In general, if you find a specimen of Scaeva like this, there are other differences on which you can distinguish S. pyrastri from S. selenitica.
Pyrastri has on its sternites bigger, square dark markings, which are broader than high.
With S. selenitica, these markings are more rounded, and these are higher than broad.
Furthermore, selenitica usually has a black ring on the hind tibia, which is absent in pyrastri!

Gerard Pennards
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23.09.21 15:29
All sorted.

16.09.21 22:24
Sorry put 5 new threads in Asilidae forum instead in Syrphidae forum, can pleas an admin move it to Syrph? THANKS, Norbert

09.09.21 07:48

09.09.21 07:47
wing ventation is totally different

03.09.21 12:51
Hi, what's the major difference between dolichopodidae and rhagionidae? Can someone help me? Thanks!

28.06.21 15:24
thx TO eklans

03.06.21 11:11
@Tony Irwin Thank you Tony! I've emailed you there Pfft

02.06.21 22:26
Rob - can you PM me with an e-mail address, and I'll send it over.

02.06.21 13:16
Hello chaps! Does anyone have a copy of: Revision of the willow catkin flies, genus Egle Robineau-Desvoidy (Diptera: Anthomyiidae), in Europe and neighbouring areas ?? I'd be ever so grateful! Rob

31.05.21 14:31
The part that got deleted is "longer, dark median stripe on thorax"

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