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A friend posted these two shots of what I am fairly certain is one of the Tabanidae, having first wondered, then accepted as such on the basis of its venation. However, I post the shots because I have never seen the like. Any ideas of genera, biology etc anyone? If not, just enjoy; Pieter Kotzee takes some fine photos.
First Photo 1.

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OK, Lateral aspect coming up, venation should be discernible (with difficulty).

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Apologies all: I got so involved in the uploading that I forgot to mention the location:
Heidelberg, Gauteng, South Africa. Google Earth Coords roughly -26.49, 28.4

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STUNNING !

No idea, never seen. Should be some Chrysops.
Any chance we can see the antenna in focus ?


Theo

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Hi, I think this is Chrysops laniger, the males of this group have long pale hairs unlike the more typical females.

Steve

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I doubt it Theo, but I'll pass this remark on to Pieter. Maybe there will be more in his area from time to time.

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Thank you Steve, I'll pass that on to Pieter. The specific epithet laniger (which I believe means "woolly" ) seems apposite. :)

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BTW, I notice that the eyes are typically masculine, with large ommatidia above and fine ommatidia below. Also, the proboscis would seem better adapted to sopping up nectar than piercing for blood (granting that I cannot see what any internal stylets might look like.) ;)

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It IS a male, if you are in doubt. Many Chnysops males have the eyes dichoptic.

Theo

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Thanks Theo, that was what I had deduced, but it is prudent to confirm one's suspicions.
Incidentally, such dichoptism, particularly among males seems to be very widespread in certain insects, generally males of flying insects, and in particular in many Diptera, though also in unrelated orders. I don't suppose that anyone in the forum happens to know of any reason why? I have a private speculation, but I'd rather not mention it before hearing what others have to say, for fear of influencing any discussion.

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Dichoptic Chrysops males can be sexed by the inner margins of the eyes. They are closely spaced and the frons is narrowest in front of the ocelli. Females have broad, nearly parallel-sided frons.

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Hi Jon, in Tabanidae the male/female proboscis is essentially the same. Stylets in the female mouth parts stab the skin and blood is lapped from the surface - like nectar! Very different method to mosquitoes.
C laniger is indeed a suitable name:)
regards, Steve

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Thanks chaps, you really are being very helpful as usual.
Possibly by way of reward, Pieter has presented another useful image, showing the antennae in better detail as Theo requested. I attach it.
Incidentally it also shows the proboscis from a more helpful angle, consistently with Steve's remarks.
John, thanks, and your description of the eyes of the male Chrysops of course matches the full-face image very well.

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Description and images of this species, laniger, in Oldroyd "The Horse Flies of the Ethiopian Region" vol III. pp 88-93

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Yes, I had finally time to grab the book and the ID is 1000 % correct !

Theo

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Much thanks everyone!