Deer flies are the bane of summer here in the Northwoods—and around the world. Only Iceland, Greenland, and Hawaii are safe. Just as the black flies become a distant memory and the mosquitoes are relegated to “mosquito hour” in the evening, the deer flies start interfering with our beautiful, sunny days above 71.6 degrees Fahrenheit.

The reason we dislike deer flies so much is that the females need a blood meal to fuel egg development. Unlike the precise, syringe-like mouth of a mosquito, deer flies have two scalpel-like mouth parts that they use to make a cross-shaped incision in your skin. Their saliva contains anti-coagulants to make it easier for them to lap up your blood with a sponge-like tongue.