SEX OF WEEVILS SURVTVING HTBERNATTON. 



91 



SEX OF WEEVILS SURVIVING HIBERNATION. 



We found it possible to readily and accurately recognize male and 

 female weevils without a partial dissection. In comparatively few 

 species of weevils are the males and females so closely similar in gen- 

 eral external character as in the case of the Mexican cotton boll 

 weevil. It was found that size depended primarily upon the food 

 supply of the larva and that it had no special significance in regard 

 to sex, although it appears that the average male is slightl}^ smaller 

 than the average female. There exists a rather wide variation also 

 in coloration, which also proved to depend upon food supply and 

 age rather than upon sex. 



SECONDARY SEXUAL CHARACTERS. 



We are indebted to Dr. A. D. Hopkins, of the Bureau of Ento- 

 mology, for indicating the most strongly marked points of difference 

 in the secondary sexual characters of the boll weevil. The distinctive 



^7^^ cf length 38mm.; t/p fomert/on /2mn7. 



O » 42 n n }J )? /8 " 



Fig. 9.— Secondar}- sexual characters of Anthonomus grandis. (After Hopkins.) 



characters (see fig. 9) are found upon the snout and upon the dorsal 

 side of the last two abdominal segments, which are normally almost 

 completely hidden by the wing covers. The differences are subject to 

 some variation but are still sufficiently constant to enable a close 

 observer to positively separate males from females with the aid of a 

 hand lens. Since these points of distinction have not previously 

 been published it seems advisable to include them here, as they fur- 

 nish the basis for the determinations of sex which follow. 



Female. — The snout of the female is slightly longer and more 

 slender than that of the male. It usually tapers slightly from each 

 end toward the middle when viewed from above. The antennae 

 are inserted slightly farther from the tip than is the case in the male. 

 The insertion is at about two-fifths of the distance from the tip of 

 the snout to the eyes. As a rule the surface of the snout is more 

 smooth and shining than in the male. A slight depression, rather 

 elongated and much larger than any of the other punctures upon the 



