As nematoceran flies, sciaroid adults generally have long segmented antennae, while their larvae have a well-developed head and mouthparts.

[3] Most fungus gnats (Sciaroidea excluding Cecidomyiidae) live in forests with their larvae occurring in fungi, dead wood and soil.

[4] Several genera of Sciaridae and Mycetophilidae may reach high abundances in damp buildings with wet organic matter.

[6] Sciaroid larvae typically feed on fungi but there are some which form plant galls (many Cecidomyiidae) or prey on other invertebrates (Keroplatidae).

[7] A 2016 molecular phylogenetic analysis confirmed that Sciaroidea is a monophyletic group and should include both Cecidomyiidae and Ditomyiidae.