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Dear forum.
I photographed several specimens of an asilid in April on Rhodes, which I thing is Antiphrisson trifarius. To my surprise, I found an Antifrisson sp. again in October
on the same island. The latter, however, looks different to me. In general, the body color of the October specimens is lighter (more yellowish than brown), bristles around the periphery of the notum and the scutellars are whiteish (instead of black), there are no black bristles on the occiput and in the mystax. I think I see a subtle difference in the shape of the ovipositor of the two as well: T8 is slightly domed dorsally in A. trifarius, whereas in the "autumn" specimens the dorsal outline of it is essentially straight. But this could be an illusion caused by looking at it in different angles.

The "autumn" specimens resemble the few images of Antiphrisson adpressus found in the Internet, which is known from nearby Turkey. Could the "autumn" sp. be identical with A. adpressus?

Thanks for any help/comment in advance!

Greetings,
Henrik

Antiphrisson cf. trifarius male:

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A. cf. trifarius female:

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Antiphrisson cf. adpressus female:

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A. cf. adpressus male in copula:

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A. cf. adpressus female in copula:

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A. cf. adpressus female, head and thorax:

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A. cf. adpressus male, head and thorax:

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A. cf. adpressus female, tip of abdomen:

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A. cf. adpressus male and female in copula, tip of abdomen:

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Up a bit...

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I realized that all hairs of the mystax of the "autumn" specimens are yellow. Using Engels key, this leads to Antiphrisson thalhammeri, which is considered to be a synonym A. trifarius. So the lighter autumn variant would simply be a color form of A. trifarius. But than it is interesting that all spring specimens I observed (4) look like "classic" A. trifarius, while all autumn specimens (3) belong to the thalhammeri form

I would greatly appreciate any opinion about this issue!

Greetins,
Henrik

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Color of Chironomidae correlates with water temperature, so the first generation of spring is darker than the summer generation. There are other possibilities here. Maybe the two generations are reproductively isolated and have started to diverge morphologically, but not so much that taxonomists consider them distinct species.

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Thank you for your reply!

Yes, temperature during a critical period of development could be the key factor.

BTW some Antiphrisson shown on Flickr under the name A. adpressus are indistinguishable of these "thalhammeri" of mine, so their identity is also questionable:

https://www.flickr.com/photos/superegnum/51453752028/in/photostream/

https://www.flickr.com/photos/superegnum/51468673209/in/photostream/

Interestingly, those photos were also taken in autumn (middle of September).