Ability of ovipositing seed beetles to discriminate between seeds with differing egg loads

Abstract. 1. Previous work has shown that ovipositing females of Callosobruchus maculatus (F.) avoid seeds already bearing eggs, and thereby reduce competition among their larval progeny within seeds. 2. This study demonstrates that females also detect small differences in egg density, and prefer to oviposit on seeds with a lower‐than‐average number of eggs. A nearly uniform dispersion of eggs is thus maintained even after all seeds bear several eggs. 3. In addition, variation in egg load influences oviposition rate. Transfer of females from seeds with few eggs to seeds with many eggs inhibits oviposition; the reverse transfer stimulates it. 4. The upper surface of the egg chorion or egg ‘cover’ remains intact on the seed surface after the larva has entered the seed and continues to deter egg‐laying for at least as long as the period required for larval development. 14‐day‐old egg covers provide as much deterrence as freshly laid eggs.