32 



Characters commoul}" used to separate the sexes in the family Cur- 

 culionidje are not distinctive in this species. As a rule the antennse 

 are inserted nearer the tip of the snout in the male than in the female. 

 This character is variable among boll weevils; and though a large 

 number of accurate measurements might show that a slight difference 

 generally exists^, it is too inconspicuous a character to be of general 

 use. With most species the top of the rostrum of the male is rougher 

 tlian is that of the female. However it may Ji)e with other species, 

 there is but little if anj^ difference in this respect between the young 

 adults of the boll weevil. As the individuals become older the greater 

 activity of the females serves to wear the roughness from the top of 

 the rostrum, and thus gradually, as a result of different habits, this 

 character becomes more distinctive. In less than half of the boll 

 weevils, however, is tliis character sufficiently noticeable to separate 

 the sexes. The terminal segment of the abdomen shows no external 

 difference in either sex, although in many weevils important charac- 

 ters are there found. 



PROPORTIONS OF THE SEXES. 



No reliable secondary sexual characters having as yet been discov- 

 ered, the cei'tain determination of sex therefore rests solely upon the 

 primary characters, thus requiring a certain amount of dissection in 

 each case. Such determinations have been made upon large numbers 

 of weevils taken in the field and upon many bred in the laboratory at 

 various seasons of the year. The results are brieflj'^ summarized in 

 Table VI. 



Table VI. — Proportions of the sexes. 



Number 

 of fe- 

 males. 



Season of 1902, both bred and from field 



Hibernated weevils, 19(J2-3 



First generation, 1903 



Bred weevils, 1903 



Field weevils, midsummer, 190'> 



Total --- --- 



From these 1,207 determinations it appears that males are somewhat 

 more numerous than females, the i^ercentage being nearly 54 of males 

 to 46 of females. It is noticeable, however, that the only season at 

 which a preponderance of males occurs is during late fall. If we 

 exclude the figures for hibernated weevils for a moment, we find that 

 the totals for the balance of the season are remarkably close for the 

 two sexes, being 380 males and 384 females. It seems safe to say, 

 therefore, that the sexes are practically equal in numbers except that 

 more males than females seem to be found among hibernating weevils. 

 It may be that the retardation of development due to approaching 



