How Big Can A Housefly Get?

This evening after returning home from work, I saw a fly in the bathroom. Not just any fly. It was huge. The thing had to be at least three-quarters of an inch long. My wife thought it might be a bee initially, but no… it was a fly. I tried (in vain) to take some decent pictures and even a video with my phone, and eventually got out the flyswatter.

Check out those eyes! (photo from Wikipedia)
Check out those eyes! (photo from Wikipedia)

Later this evening while mowing, I started thinking: How large can a housefly grow? What makes flies grow so large? I had a pretty good suspicion that some exotic and jungle-filled country probably had the world record for the largest species of fly, and it was probably big enough to be counted as a bird. So, after finishing cutting the lawn and reading a chapter of our current read-aloud book to the kids, I pulled up the internet to do some fly research. Turns out there are definitely larger species than our common housefly. This article from the BBC had some really interesting information on the topic, including facts like:

  • The largest fly, called a Mydas Fly, measures around 7-8cm (2-3 inches). Eew.
  • Flies are likely limited in how large they can grow due to the temperature of the earth.
  • There’s a really long-legged species of fly that, when stretched-out, could be almost 23 cm.
A photo of a Mydas Fly from Wikipedia
A photo of a Mydas Fly from Wikipedia

So, I guess my fly wasn’t so large. But it still was cool to chase around and look at, and also fun to spend my lawn-mowing time wondering about houseflies.