The large mosquito-like insects are crane flies. Crane flies and mosquitoes are closely related but are in separate families within the true flies (order Diptera). Crane flies have thin bodies and long, slender legs that are easily broken.

Although they may resemble mosquitoes, they will not bite or sting. The adult crane flies usually live only for a couple of days. Adults may feed on honeydew or nectar.

Crane flies are not typically found in houses. They prefer living in moist, humid environments. The larvae of some crane fly species prefer moist soil whereas other larvae species prefer aquatic environments. Crane flies usually overwinter as pupae. If you see adult crane flies in your house during the winter, the larvae probably overwintered in the soil of houseplants. If your houseplants were outside during the summer, the adult crane flies probably laid eggs in the damp soil. The eggs hatched into larvae which are often called "leatherjackets" because they have tough skins. The larvae feed on decaying organic matter.

Preventive measures should not be necessary. You will not realize that you have crane flies until you see them flying around in your house. Crane flies do not commonly occur indoors. They will not damage houseplants or infest food or clothing. The adults are temporary nuisances that can be swatted and vacuumed. It is unlikely that crane flies would reproduce inside because most house environments are too dry.