Trees are dormant, days are short, and it’s cold outside. You’re warm and cozy at home, enjoying a little down time, when suddenly you hear a loud buzzing noise. Something shiny darts past your face on its way to the window. It’s a blow fly!

Immediately you wonder “What’s the deal? It’s winter! Aren’t flies supposed to be hibernating or something?”

Blow flies (sometimes called “bottle flies”) can make an appearance any time unsanitary conditions exist around your property. Blow fly larvae (a.k.a. maggots) thrive on trash, waste, and sewage. When you see them, especially in the winter, it’s time to clear the place their larvae are growing! But first, you need to find their feeding ground!

Start by inspecting garbage cans. It’s possible your trash hasn’t been removed often enough, or that debris remained after cans were emptied. Blow flies frequently lay eggs in meat and vegetable scraps inside and around trash receptacles. After the eggs have developed into larvae and eaten their fill, they often crawl into dark, secluded places to pupate.

Also, check for sewage seeping from pipes, either at the joints, or from cracks in the pipe itself. Blow flies love to lay eggs in soil soaked with wastewater.

Animal carcasses can also produce a flush of flies. Perhaps there’s a dead mouse in a forgotten trap, or a rodent has expired inside your walls. Larger animals (squirrels, birds, raccoons, etc.) that die in your attic or chimney are also great food sources for developing larvae.

Important note! If you discover a carcass inside a wall, think carefully before breaking out the wrecking tools! Blow flies are only interested in “fresh” cadavers. They will stop laying eggs and feeding within a short time. (However, other insects like rove beetles, carpet beetles and hide beetles may be drawn to older remains.)

You may wonder if it’s worth the trouble to find and remove blow fly habitats. The short answer is “yes!” Two reasons…