Diptera.info

Posted by conopid on 23-10-2009 11:42

Dear forum,
I have a British specimen of Xanthogramma, which I believe is X stackelbergi. I have concluded this from the English keys and key-facts in the Encyclopedia of the Swedish Fauna & Flora series - Tv�vingar: Blomflugor. I am fairly confident that my specimen is X stackelbergi, but I need to get this validated.

If this is indeed X. stackelbergi, it would be new to Great Britain.

Two questions:
1. There may be further information that can further clarify my determination, contained in the more extensive Swedish text. Is there anyone able and willing to translate the text, in the above volume, about X stackelbergi from Swedish to English for me? It's about 2-300 words I guess.

2. Is there anyone I can send the specimen to, who has access to specimens of X stackelbergi, that they can compare my specimen to?

Posted by conopid on 23-10-2009 12:41

Jari and Andre thanks for your quick and helpful responses.

I'll contact Dieter to see if he can help further.

From what Andre says, it appears that definitive determination will be difficult. However, whether the specimen is stackelbergi or dives, it would still be new to Great Britain. But it looks like it may not be possible to determine the species accurately?

Edited by conopid on 23-10-2009 12:49

Posted by Andre on 23-10-2009 13:55

From Syrph the Net, volume 2008:

Xanthogramma dives (Rondani), 1857
Range: at present uncertain, due to confusion with related species, but known from Spain, southern France (to as far north as the Paris basin), central Germany and northern Italy.
The name dives (Rondani) appears in Peck (1988) as a synonym of X.pedissequum.
Its use here is based on unpublished information received from Kassebeer (pers.comm.). Whether or no the correct name to use for this taxon is dives Rondani could only be confirmed by examination of the type material of dives. There are no clear differences between the concept of X.dives as applied here and X.stackelbergi, to judge from the rather inadequate information available about X.stackelbergi in existing literature. But, for now, the name dives is used here to draw attention to the existence of this taxon and to enable its separation from X.pedissequum.

Xanthogramma pedissequum (Harris), 1780
Range: uncertain, due to confusion with related species, but from from Britain and Atlantic seabord countries south to the Paris basin and into central Europe to the Alps (France, Switzerland).
Determination: This species is included in various keys e.g. van Veen (2004), none of which can, however, be used to separate this species from X.dives. The adult insect is illustrated in colour by Colyer and Hammond (1951), Haarto and Kerppola (2007), Kormann, Stubbs and Falk (1983), Torp (1984, 1994) and van der Goot (1986).

Xanthogramma stackelbergi Violovitsh, 1975
Determination: the description of this species is based on a solitary male from the St Petersburg region of European Russia. The female remains undescribed. X.stackelbergi is included in the keys provided by Violovitsh (1975), who also figures
the male terminalia. From the information provided by Violovitsh (1975) there would be no reliable way of separating this species from the taxon referred to in the present text as X.dives.

Posted by conopid on 23-10-2009 14:44

many thanks for this Andre. It's very helpful. I looked at Syrph the net website, but failed to find this data. What's the link for these pages?

For now it looks like separating the species is a lost cause!

It's interesting that Finnish and Swedish authors treat X stackelbergi as a species that can be determined without complication.

I guess I'll have to treat mine as Xanthogramma dives/stackelbergi - indeterminate.