@keepcalmandcarrieunderwood submitted:

@keepcalmandcarrieunderwood submitted:

It was like an all black bumble bee. Spotted in Aloha Oregon. Very chill bug

Very nice, you spotted a FLY! (Remember when I said “If you think it’s a bee, it’s probably a fly”? Also, great job going out and looking for things! I’m proud of you!) Some of these guys can get so big they are often mistaken for large bees (and that may be on purpose, too!). I am still trying to learn my flies (there are so many kinds of flies you have no idea), but I think you have either a tachinid fly or a blow fly.

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Left: A tachinid fly (I think?) [link to iNat page]; Right: A blow fly (Genus Calliphora) [link to iNat page]

Tachinid flies are common parasitoids–I’ve had a bunch hatch out of my moth cocoons when I was expecting, well, moths. Blow flies tend to lay their eggs on “gross” stuff like poop, dead animals, and can also be parasites. As far as telling them apart, I know that tachinid flies have super bristly butts. Besides that, I usually just post photos to iNaturalist and hope the fly people see them.

But how do you tell a fly from a bee? Some flies are very convincing, but there are a few things you can look for! Here are a carpenter bee and a bumble bee:

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On the left is a carpenter bee, and on the right is a bumble bee. They are both very large bees, and they can both be mostly black, or black and yellow. The key difference is carpenter bees have shiny bums and bumble bees have furry bums. I point out some key features on the carpenter bee for comparison with flies: bees have long antennae, fat legs (to carry pollen!), and black eyes. The thing about the eyes may not be universally true for bees, but compared to flies…

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Above is what I think is a tachinid fly [link to iNat observation]. The big giveaway is the antennae. I call fly antennae dongles because I can. I don’t know the technical term. In any case, they are placed where you would expect a nose (instead of their “forehead” like bees). They also have skinnier legs, and many have red eyes. Also, check out those hairs. With bees, you either have fluff/fuzz or smooth. You don’t have hairy/bristly bodies, but they are common on flies.

Another key differentiating feature is the number of wings, but I don’t think that’s too helpful for comparing flies and bees. The way bees hold their wings, you can rarely see that there are two. Flies will have little organs for balance called halteres (these are actually their “vestigial” second pair of wings), but they aren’t always visible. If you have a dead insect, it’s easy enough to check this, but when you have a live one buzzing around flowers (flies are very important pollinators!), it’s not as useful. Better to look at the face!

July 6, 2018
Bees and flies were all seen in Texas EXCEPT the blow fly was in San Francisco!