Help! We have recently discovered these large bright green insects which look like flies all over our 2 pet pigs. We have seen them twice & only around dusk. We have recently moved to a 46 acre farm in rural North Central Florida & the pigs are in an area that is mostly woods. They appear to be biting flies & sound a little buzzy. They act like deer flies & do not return to the pigs (on that day, at least) when they are sprayed with a pyrethrin insect repellant. I have not engaged in mortal combat with one so I have no photo yet. I’d love to identify them before we move our goats & horses here. Any help in identifying them would be appreciated. Thanks in advance,

Hi Sandra, We would love to get that photo when you go to war. We are thinking you might have Sweat Bees, which are often a brilliant green color. they are attracted to sweat, hence the name. Bees have four wings while flies only have two wings, should you ever get close enough to notice.

Thanks for the prompt response, but I think that they must be something different for three reasons: 1) I looked up some photos of sweat bees online & they didn’t look like that. 2) I was on stakeout at dusk today, but none showed up. I was visited by 2 deer flies & the ones I’m trying to identify are at least 2 – 3 times the size of a deer fly & sweat bees are supposed to be pretty small. 3) Pigs don’t sweat. (Technically they do sweat on their noses, but these guys were not near their heads, they were on their sides like a deer or horse fly would be.) Will keep on the lookout & capture dead or alive for future photo ID. Thanks again, Sandra

Here are the photos of the fly I grabbed off the pig tonight. I froze it before photographing.

Hi Sandra,
I wanted to reply to you quickly so that you would know I was working on your question. You have some type of Horse Fly, Family Tabanidae, which also includes Deer Flies. I have found references on the internet to Green Horse Flies being troublesome in Maine, and also to their proliferation in hot weather at the St. Elizabeth’s Medical Center in Kentucky, but no species name or photos. I have a query out to the Museum of Natural History in Los Angeles and hope to hear back soon. Female Horse Flies are the blood suckers while males feed on nectar and pollen. The larvae are usually aquatic.

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