Large fly for ID - Looks a bit like a horsefly!

[ronx]

DOES ANYONE Know what these flies are? We have THOUSANDS that come into the house and die every summer. They are quite big and have big mouth pieces but do not seem to bite. They look very like horseflies but are bigger. We live in woodland/grassland on chalk downs on Dorset Wilts border (Cranbourne Chase) and I am keen to ID these monsters. They don't appear in cool rainy weather. Our house is painted pink which I think also attracts them.

ANY IDEAS???

[Dogghound]

They are Horseflies Tabanus sp im pretty sure these are Tabanus autumnalis. The females do bite, not something I would want in great numbers in my house, interesting that they arnt biting though. Perhaps they breed near you and come into your house after breeding in which case they would not bite. Do you have any ponds, boggy areas, animal dung etc near you? The colour of your house is unlikely to have much influence on them.

[pressld2]

I think it is a horse-fly and Thereva nobilitata would be my suggestion. The last photo is the clearest and that one is a male - the eyes are touching. The males are nectar feeders and don't bite. It looks like a female on the window next to the ruler though!

Don't know if pink attracts them. It might do for the males I suppose if they think your house is one enormous flower!

Dave P.

Edit: Just seen Dogghound's response and I'd go with his ID. He's waaay more knowledgeable than me!

[Geoff F]

Male horseflies don't bite. Tabanus sudeticus is the largest a which can reach 25 mm. Tabanus bromius is a little smaller at 15 mm. While Tabnanus bovinus in in between at 20 mm.

They vary quite a bit in colouration and I'm no expert with this species but the leg colours do appear to resemble T. sudeticus.

But I would like a second opinion from someone who is more knowledgeable on this family.

ps. While I was checking my books, the experts have arrived, and T. autumnalis could well be the one that matches best.

[Dogghound]

autumnalis is usually associated with marsh, wet meadows, damp moorland and coastal marsh which is very different from chalk downland which is usually well drained. Size and morphology match though.

[ronx]

Thanks everyone! I have now had a really close look at one and it has a red stripe across its eyes so I am thinking maybe it must be Tabanus bromius. I can't imagine it is the autumn ones because we have no ponds, no marsh, no water at all round here - the nearest small pond is about 1/2 mile away.

They don't seem interested in biting at all, they just come into the house in vast numbers and die. They buzz quite noisily unlike the horseflies in the woods that bite so damned hard!

Thanks - I hate not knowing what something is.