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Colorful Fly - Spilomyia alcimus

Colorful Fly - Spilomyia alcimus
Assunpink WMA, Monmouth County, New Jersey, USA
July 10, 2003
Since finding this fly two years ago, I've been back to the same spot many times, but have never found another of its kind.

Images of this individual: tag all
Colorful Fly - Spilomyia alcimus Colorful Fly - Spilomyia alcimus

female Spilomyia alcimus!
Hello all,
I think this is a Spilomyia for sure, and the species is Spilomyia alcimus. Characteristic is the large amount of yellow on it's abdomen, and the number and position of the yellow spots on the side of the thorax.
Gerard Pennards

F. Christian Thompson...
of the USDA has confirmed the species of this fly as Spilomyia alcimus. Thanks Gerard.

Will move to guide to S. alcimus
Neat, I'll move this to a new guide page--I don't think this species is in the guide yet.

Patrick Coin
Durham, North Carolina

Syrphid, Spilomyia?
Looks like genus Spilomyia, though if it is, I'm not sure what species. Looks more brightly colored than the S. longicornis I've seen. There are some other species, but I haven't seen any checklists for your area.

Beautiful photos.

Patrick Coin
Durham, North Carolina

Mostly I just wanted to compliment you on the magnificent shots, especially the facial portrait. Great job! I can barely catch these flies with a net:-) Pretty sure it is a Temnostoma sp, but will keep looking.

(I'm wrong, cool)--Temnostoma links
Insects of Cedar Creek has Photos--you just don't see the funky eyes on the specimens, I guess.

Some others:
Cirrus Images--that one does not have the partly pigmented eyes.

Patrick Coin
Durham, North Carolina

Would rather say Spilomyia, but...
based only of my knowledge of the west palearctic fauna. What I can say is that every Temnostoma species of this region has all dark compound eyes, and that such yellow-striped ones are peculiar tho Spilomyia in Europe. Moreover, the pattern of the yellow stripes and spots on the thorax matches better with the latter genus - although Temnosotma has a very similar one.
Now, whether Temnostoma or Spilomyia, I agree that this one species is really superb. It seems to mimic the queen of Vepula squamosa, just like S. fusca mimics Bald-faced Hornets. If so, New Jersey is on the northern limits of its range, therefore it is quite logically a rather rare species there. On the other hand, it is not unfrequent for species of this group, in Europe, to be fairly common some years and very rare for several following season. This could have something to do with their life cycle, especially at the larval stages - which live in rotten wood.

Key from Syrphidae Oklahoma
Spilomyia and Temnostoma are keyed in Syrphidae of Oklahoma:

5. Anterior cross-vein quite oblique, and near end of discal cell, anal cell with long petiole drawn out along wing margin; medium to large (11-22 mm), often brightly marked flies-->6 (Spilomyia and Milesia)

Anterior cross-vein less oblique and at or slightly beyond middle of discal cell, anal cell with short, straight petiole; somber or brightly colored flies --->7

7 Bright, wasp-like flies, with yellow-pollinose -->Temnostoma

Further details in the description might separate these two as well. Of course, it is a key for Oklahoma species, but might still be useful.

Quoting from description of Spilomyia: eyes with vertical, irregular stripes or blotches; first and second antennal segments slightly to distinctly elongate; See this image?

and Temnostoma:
first and second antennal segments always quite short; face usually quite concave, especially in females, less so in males; males often with weak tubercle, face never deeply produced;
See this image?

Perhaps those antennal segments would separate the two genera? I think I see the difference on the images above, and on these below:

See also: Cirrus Images--Temnostoma. Maybe I see what they mean, seem to have real short first two segments. I think they are longer in the photo above, but am not experienced at this.
(Cedar Creek has one, it is down right now.)

Patrick Coin
Durham, North Carolina

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