Why are Giant Mosquitoes Swarming My House?

Maybe you're wondering why so many huge mosquito-looking bugs are flitting around your yard and getting in your house right now.

Crane flies, also known as mosquito hawks thanks to their resemblance to giant mosquitoes, are out in force right now. You may see these large flies with stilt-like legs bouncing into the walls, your lights and even bathtub (as they search for wet places to lay eggs). As insects they have six legs, which often are so delicate they break off easily.

Don't panic. Crane flies are harmless insects that do not bite, sting or transmit diseases to humans or animals. They primarily feed on nectar. In fact most do not even have functional mouth parts.

They are abundant after particularly wet winters because the conditions are so favorable for their larvae that live in water or wet soil.

Crane fly larvae

A crane fly lays eggs in low-lying areas near water, which hatch as larvae. These larvae are called leather jackets and are brown or gray and cylinder-shaped. They have finger-like projections on one end, no legs, and don’t have a head. Common and European crane flies of the Pacific Northwest eat shoots, roots, and leaves in your lawn. 

Eventually, they become pupae in the soil and emerge as adult crane flies, leaving the casing behind in the lawn. They spend anywhere from a few months to a few years in that larval stage before they go through a pupation, like caterpillars, and emerge into the adult stage that flies around looking for mates.

Their only job as an adult is to find mates and then lay eggs back in the water or wet soil where they came from. Adult crane flies sometimes feed on nectar but mostly don't eat anything. They spend their adult life mating and laying eggs and then die.