Can flies survive the winter?

You come home after being out in the bitter cold, and there's a fly. How'd it get there?
10 May 2021
Presented by Adam Murphy
Production by Adam Murphy.


A fly


Jeffrey got in touch to ask: "We’ve had a cold and snowy winter, and I’ve had to shovel my driveway every few days. We had a fly in our house, and I was curious if it survived the cold somehow, or recently hatched?" Adam Murphy got in touch with Erica McAlister, fly specialist and Senior Curator from the Natural History Museum in London to fly in an answer...

In this episode

A fly

00:00 - QotW: Where do flies go in winter?

Despite subzero temperatures outside, they still appear and buzz about your house. Where do they hide out?

QotW: Where do flies go in winter?

Adam - We’ve all been  there, it’s been a cold winter, and everything seems dead, but then you stomp inside from the cold, and there’s already a fly buzzing around, enjoying having a nice warm room and a human to annoy. Where do they come from? Well, Erica from the Natural History museum has some thoughts on the origins of the buzzing suspect.

Erica - First off, to comment properly on the specifics of your fly, we would need to see it to identify it.

Adam - Ah. Not so easy to pin down then

Erica - However, there are four scenarios for your hardy beast

Adam - Oh good, so what’s the first option Erica?

Erica - 1) It is an overwintering species that has come out early. Many flies overwinter as adults – some really hairy beasts include cluster flies (they do indeed hurdle together) but many others find a warm place and hunker down including many female mosquitoes. The first will stay put most of the winter but many, including the latter, will take opportunities to feed if the conditions become favourable.

Adam - I also feed whenever conditions are favourable, so I understand that, but some of these flies will still be growing…

Erica - 2)The majority will be snuggled up and metamorphosing in their pupal case or puparium. Flies are some of the earliest to emerge in spring and they may have been tricked by some environmental trigger (your house?) into believing conditions were favourable.

3) Then there are the completely badass flies that do not regard cold/snowy conditions as an issue. (In the arctic 4000 species of insect have been recorded – 2000 of them are flies). These could be cold adapted species

Adam - And of course, if a fly doesn’t like the cold, there’s one obvious refuge it might find…

Erica - Number 4. They could be very anthophilic (human loving) species who can use our environs for their own – we provide lots of heat, shelter and food for them to survive

Adam - Thanks to Erica McAlister for flying in that answer. Next time, we’re answering this burning question from Trent…

Trent - I just got back from walking my dog. Now, about a block from my house, there's a trailer that's been parked there for a year or two and every time we walk by, the dog pees on the same tyre. It got me thinking: Urine contains uric acid, is that strong enough to eat through the rubber in the tyre? If so, how long would it take?


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