Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Suborder: Nematocera
Infraorder: Psychodomorpha
Superfamily: Anisopodoidea
Family: Anisopodidae
Common names:  Window gnats, Wood gnats,

The Anisopodidae is a small cosmopolitan family of gnat-like flies with a worldwide distribution. They are mosquito-like but the proboscis shorter than the head. Some species have dark spots on their wings.
Their larvae are found in or near decaying wood or vegetation, fermenting sap, animal manure, tree trunks, mud, and sometimes sewage
Adults are found on foliage or around flowing sap in or near damp places; sometimes seen in swarms and may be attracted to light.

A 4 mm long gnat in the family of Anisopodidae
Gnat Family Anisopodidae window gnat.JPG 

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0