Adults of the anthomyiid Coenosia tigrina (Fab.), which are predators of flying insects including pest Diptera such as the onion maggot fly, feed on earthworms in the larval stage. The bionomics of C. tigrina females were studied in the laboratory at 15, 20, and 25°C, under different mating regimes. Adult female longevity slightly exceeded 1 month at 25°C and was close to 2 months at 15°C. Oviposition started 1–3 weeks after emergence, the delay tending to decrease with increased male presence. Females laid eggs at intervals of 1 to several days, in batches averaging 10–30 eggs depending on temperature. Fecundity reached an average of 230 eggs at 25°C with the sustained presence of males. Egg hatch decreased with the mother’s age, except when males were present for most of the female’s lifetime. Females exhibited maximal daily rate of predation at 25°C, but maximal lifetime predation was observed at 20°C. Male predation was less than females’, and female predation decreased with age. The time to eclosion decreased from 11 to 5 days as the temperature of egg incubation increased from 15 to 25°C. Larval weight at eclosion decreased with mother’s age. Postembryonic development and larval growth were studied at 15, 20, and 25°C, larvae being fed on four lumbricids. Development times decreased with increasing temperature between 15 and 25°C: from 35 to 15 days for larval development, and 28 to 12 days for pupal development. Males developed at a slower rate than females, but females weighed more at emergence. Larval survival was 30–60% on worm sections, and dropped to 17% on live mature Eisenia foetida (Sav.); but survival reached 90% on live, immature E. foetida 1–2 cm long. The larvae of C. tigrina penetrate the epidermis of earthworms, and feed internally with a preference for circulatory and chlorogogonous tissues.