In Acanthoscelides obtectus (Say) (Coleoptera, Bruchidae) several first instar larvae can use a hole made in the seed coat by a conspecific to enter the seed. The present study tests whether there exists different seed-coat piercing abilities related to the hatching rank. The hatching rhythm was found to be well synchronized with the periodic conditions. The hatching rank had no influence on the piercing behaviour. On the basis of these observations the hypothesis of a behavioural dimorphism as has been suggested in the literature may be rejected.
