Cluster Flies

As many people living in the country have learned the hard way, flies that gather in windows, buzz around the lights and fall spinning to the floor are cluster flies.

Their presence solicits anything from mild annoyance to putting a for sale sign on the front lawn. To understand the problem, it helps to know a little bit about the habits of these flies.

Cluster flies are different from most of the other flies that we encounter.

First, they are parasitic on earthworms, their life cycle taking place in the soil of fields and lawns.

Second, they are long lived, over wintering in various places or structures such as homes and emerging in the spring. Females lay their eggs in the soil and the larvae ( maggots) seek out and penetrate earthworms.

After 15 to 20 days the maggots leave the worm, move near the soil surface and pupate. The cycle can be completed 3 or 4 times in a season.

The adult flies feed on the nectar of flowers.They simply enter structures in the fall in order to try and over winter. Once inside, while it is cold they remain dormant. Unfortunately on sunny days, even in winter, they will become active and end up coming out inside the house.

They are often found at windows because the light from outside is attracting them. Late fall and early spring are when the flies tend to be most numerous in homes. If you think your problem is bad, one structure was reported to have a quarter of a million flies. That's a lot of vacuuming!