Caenotus

Caenotus can be distinguished from other Scenopinidae by the combination of: reduced wing venation with loss of the discal cell; elongated, slender body form; and the structure of the male genitalia. It differs from the related genus Scenopinus by its more slender build and specific wing vein reductions. Species-level identification requires examination of male terminalia and is best confirmed by specialists.

Arid and semi-arid environments including deserts, dry grasslands, and scrublands. Adults are often found on vegetation or near the ground in dry, open habitats. Larval habitats are poorly documented but are presumed to be associated with dry, decaying organic matter or soil.

Primarily distributed in arid regions of the Americas, with records from the southwestern United States and Mexico. Some species extend into Central America. The genus shows a preference for xeric habitats.

Adults are most commonly observed during spring and early summer in temperate regions, with activity extending into summer and fall in warmer areas. Activity patterns likely correspond to moisture availability and temperature.

Complete metamorphosis with egg, larva, pupa, and adult stages. Larvae are presumed to be predatory or saprophagous in soil or decaying organic matter, though specific details are poorly documented for most species. Developmental timing varies with environmental conditions.

Adults are diurnal and often observed running on vegetation or the ground rather than flying. They are weak fliers and tend to remain close to the substrate. When disturbed, they may make short, erratic flights before landing again.

Presumed predators as larvae, contributing to soil food web dynamics in arid ecosystems. Adults may serve as minor pollinators or prey for larger arthropods and small vertebrates, though quantitative data are lacking.

No direct economic importance. Occasionally encountered by entomologists in pitfall traps or sweep samples from arid habitats. Not known to be pests or vectors of disease.

• ScenopinusAlso in Scenopinidae but generally more robust with better-developed wing venation and different male genitalia structure.
• RhyacophilaDifferent family (Scenopinidae vs. Rhyacophilidae or other groups); Rhyacophila are caddisflies (Trichoptera), not flies, with hairy wings and aquatic larvae.
• BibioBibionidae are more robust, humpbacked flies with distinctive wing venation including a large discal cell and different antennae structure.

• Diptera
• Scenopinidae
• window flies
• arid habitats
• North America
• predatory larvae

• BugGuide
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life