SEXUAL DIMORPHISM IN THE SWEET-POTATO WEEVIL, CYLAS-FORMICARIUS (F) (COLEOPTERA, BRENTIDAE)

Cylas formicarius (F.) shows a strong overall sexual monomorophism, wi th external differences noted in only three organs: (a) relative size of the hind wings; (b) form of the antennal club and numbers of its di fferent types of sensillum; and (c) size of the compound eyes and thei r individual facets. We relate these to known or predicted behavioural differences. Eye dimorphism is used to test a theoretical rule on the relationship between differences in overall eye size and in the size of individual ommatidia. Some sexually monomorphic features are briefl y discussed, including two types of putatively sensory hairs not found on the antennae.