Seasonality
for Drain Fly
Indoors, where pipes stay warm and food never runs out, drain flies can reproduce continuously and persist indefinitely, often turning up in seldom-used drains while a home sits empty. Source: https://extensionentomology.tamu.edu/wp-content/uploads/2017/09/Drain-Flies-Publ.-E-184.pdf Source: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/ENTO/ENTO-414/ENTO-414.pdf Outdoors the pattern is seasonal: adults appear in early spring and peak in late summer in temperate regions, slowing in colder months. Source: https://ask.ifas.ufl.edu/publication/IN1226 Source: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/ENTO/ENTO-414/ENTO-414.pdf