Adult emergence in the sorghum midge,Contarinia sorghicola(Coquillett), is a singlephase diel rhythm with peak eclosion 1–2 h after sunrise, Males began emerging 30–45 min earlier than females and by the time the latter reached peak numbers, male emergence was 85% complete. Males began emerging at 55–60°F (12.8–15.6°C) and females at 65–70°F (18.4–20.1°C). Emergence of both sexes ceased at 95°F (35°C). The sex ratio was near 1:1 early in the season (Aug.) but by October females outnumbered males ca. 2:1.Females dispersed to susceptible florets and oviposited until death. Males continued to swarm around head from which they emerged and were not associated with blooming heads.