RECENT STUDIES OP THE MEXICAN COTTON BOLL WEEVIL. 11 



squares, leaves, or bolls. In each lot the weevils were paired off 

 together for a few hours daily while under close observation. As 

 soon as a pair copulated they were removed from the lot and the 

 remainder tested until they either copulated or died. In this copu- 

 lation series 23 pairs of weevils fed on squares, 2 pairs fed on bolls, and 

 1 pair fed on leaves copulated. These figures are of more value when 

 taken in relation to the number of pairs of weevils that refused to 

 copulate before death on the different foods. This relation is shown 

 in Table III. 



Table III. — Relative proportion of boll weevils copulating on different foods. 



Food. 



Number pairs 

 of weevils 

 carried to 

 either copula- 

 tion or death. 



Number 



pairs 

 copulated. 



Percentage 

 copulated. 





38 

 8 



8 



23 

 2 

 1 



Per cent. 

 GO 





25 





12 







From this table it is seen that copulation is unusual when the 

 weevils are fed strictly on either cotton bolls or leaves. 



AGE AT WHICH FERTILIZATION TAKES PLACE. 



The length of the period before copulation depends in a large 

 measure upon the temperature as well as upon the food. For square- 

 fed weevils this period varied from 3 to 10 days, with a weighted 

 average of 5.8 days. 



In the series of boll-fed weevils only two records were made on 

 this period. Both of these were in the latter part of June and were 

 6 and 8 days, respectively, giving an average of 7 days. 



In the leaf-fed series only 1 pair copulated, and they gave a period 

 of 5 days. 



The records on boll-fed and leaf-fed weevils are too few in number 

 to offer any comparison with the length of the period for square-fed 

 weevils and serve only to emphasize the difficulty with which the 

 life functions are performed on these unnatural foods. 



The period from emergence to copulation was not determined 

 exactly for the weevils fed only on buds and blooms of Hibiscus 

 syriacus, but some idea of the period can be secured from the first 

 date the weevils were observed in copula while making the daily 

 examination. Two pairs of A. g. ihurberise were first observed in 

 copula in 6 and 14 days after emergence, while at the same time 

 (September) two pairs of A. grandis were first observed in copula 

 in 9 and 13 days after emergence. These records and the frequency 

 with which the weevils were observed in copula later show that the 

 proper element to stimulate copulation is present in the food. 



