A Note on Sexual Dimorphism in Sitophilus Weevils

Abstract

The advantages of being able to determine the sex of insects by means of external characters are obvious, particularly when, as with the Sitophilus weevils, they have been favoured as experimental material by many workers. In Sitophilus oryza (L.), the sex can apparently readily be determined by reference to the relative length of and type of puncturing of the rostrum (Richards, 1947). There has seemed, however, to have been some doubt about a similar reliable method of determining sex in Sitophilus granarius (L.). Richards (1947) stated that there was no certain way of determining the sex of this species without risking injury to the female. In a later paper (1948) he implied, in a footnote, that a specimen could be sexed by reference to the length and slenderness of the rostrum. This had been given as a method of sexing these insects by Back and Cotton (1926).