52 THE MEXICAN COTTON-BOLL WEEVIL. 



From these determinations it appears that males are somewhat 

 more numerous than females, the percentage based on our observa- 

 tions being 57.2 males to 42.8 females. It is noticeable also that the 

 males are in preponderance throughout the year. Since the males 

 are less active in their movements than are the females, the advantage 

 of the existence of the majority of males becomes apparent. The 

 larger number of males and the more active habits of the females 

 serve to increase the chances for the meeting of the sexes. 



It has been shown by rearing experiments conducted at low tem- 

 peratures that the retardation of the development, such as is due to 

 cold weather, favors the development of the males. 



FERTILIZATION. 



AGE AT BEGINNING OF COPULATION. 



After the adult weevils have left the squares a certain period of 

 feeding is necessary before they arrive at full sexual maturity. 

 This period varies in length according to the temperature prevailing 

 and appears to bear about the same ratio to the developmental period 

 as does the pupal stage. With weevils fed upon leaves alone the 

 period preceding copulation is about twice the normal length, in the 

 cases observed, of those having squares to feed upon. Mr. Cushman, in 

 observations at Tallulah, La., in 1910, found that the period from emer- 

 gence of the female to copulation varied from two to seven days, with 

 an average of 4.4 days. During hot weather it is probable that this 

 period averages three or four days, but as the weather becomes colder 

 it increases gradually until the weevils may become adult, feed for 

 a time, and go into hibernation without having mated. It should not 

 be understood, however, that weevils do not usually copulate before 

 hibernation. Mr. C. E. Hood made numerous observations of the 

 exercise of this function in the fall of 1909 at Mansura, La. 



SEXUAL ATTRACTION AND DURATION OP COPULATION. 



The distance through which the attraction of the female insect will 

 influence the male varies extremely. In observations made by Dr. 

 Hinds at Victoria, Tex., it was found that the male was unable to 

 recognize the female at a much greater distance than an inch. Obser- 

 vations carried on in the field, as well as in the laboratory, tend to 

 show that the sexes are attracted only when they meet, as they are 

 likely to do either on the stems or upon the squares of the plant. 



In a considerable number of cases that were timed the average 

 duration of the sexual act was very nearly 30 minutes. The earliest 

 spring records of copulation available are for April 15. 



DURATION OF FERTILITY. 



A number of femaies which were known to have mated were isolated 

 to determine the duration of fertility. Although the limit was not 

 determined exactly, the results proved very striking. Several of the 

 females laid over 225 eggs each, and nearly all of them proved fertile. 

 Selecting three cases in which the facts are positively known, it 

 appears that fertility lasted for an average of something over 66 days 



