Ovarian growth was delayed at least 25 d in females of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), fed sugar cubes containing J2581 (5-ethoxy-6-[4-methoxyphenyl]methyl-1,3-benzodioxole) at a concentration of 0.57 mg/g. Ovarian development of females fed a sugar-protein hydrolysate diet containing the same concentration of J2581 was delayed by 9 d. Egg hatch (larval eclosion) was significantly reduced from 0 to 6%. Eggs that failed to hatch had fragmented yolk plasm and absence of embryonic development. Ajuvenile hormone analog, (7S)methoprene, concomitantly fed with J2581 to newly emerged flies, caused partially increased oviposition but no improvement in ovarian growth or percentage egg hatch. J2581 and seven other benzyl-1,3-benzodioxoles were not mutagenic in the Ames Salmonella microsome test with and without metabolic activators.