The biology ofLiriomyza sativaeBlanchard on castor bean,Ricinus communisL., was studied. Host preferences ofL. sativaeandL. trifolii(Burgess) for castor bean and celery,Apium graveolensL., were determined. Total developmental times for the immature stages ofL. sativaereared on castor bean varied from 13.1 d at 30°C to 28.5 d at 20°C; pupal development lasted slightly longer than the combined egg and larval stages.L. sativaefemales produced a mean of 164.5 larval progeny at 25°C on castor bean during an average lifespan of 13.4 d. Fecundity peaked at age five days.L. sativaefemales strongly preferred castor bean over celery for oviposition; no progeny were produced on celery. In contrast,L. trifoliiproduced about four times as many progeny on celery as on castor bean.