Black tachinid fly - a beneficial fly (it's not a housefly)

I photographed this tachinid fly while on a walk in Kelowna, BC.  March 21, 2026.

Yes, it kind of looks like a housefly.  But it's not.  You can tell because of the long hairs coming off its abdomen (back end).  This is a tachinid, a kind of fly that is a parasitoid, meaning that it parasitizes its host and ultimately ends up killing it.  The thing is, its larvae devour harmful insects.

The hosts of most tachinid flies are the larval stages of insects showing complete metamorphosis.  For example, some tachinid flies are parasitoids of caterpillars.  Harmful insect species such as gypsy moths, armyworms, and tent caterpillars can be controlled through tachinid fly propagation.  However, each fly species has its own particular species on which it lays eggs.

So, if you see a fly with a hairy rump,
Do not kill it with a swatter or thump.
Instead, set it free and let it carry on,
'Cause it is beneficial through predation.

Well, I tried.  Thanks for reading.

Eric Svendsen     www.ericspix.com

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