33 



cold weather favors the development of males. Not only was there a 

 larger number of males than of females taken in December, 1902, but 

 there were also more males than females taken in the field in the spring 

 of 1903 among the hibernated weevils which lived through the winter. 

 According to the determinations made, 64 per cent of the 259 weevils 

 dying during the winter were males and 56 per cent of the weevils liv- 

 ing through the winter were also males. Since it appears that females 

 require fertilization in the spring before they begin to deposit eggs, 

 the preponderance of males at that time acts as a provision to insure 

 the propagation of the species. 



LENGTH OF LIFE UPON SQUARES. 



The observations made along this line may be divided into eight 

 groups, each dealing with some special food condition or class of 

 weevils. For the confinement of weevils in the laboratory the most 

 satisfactory apparatus tried, both for convenience in handling and for 

 the maintenance of favorable conditions for the weevil, was made up 

 as follows : A 4 or 5 inch shallow earthen saucer, such as is used with 

 flowerpots, was filled with soil, which was kept fairly moist. Over 

 this was placed a fresh cotton leaf, which conserved the moisture from 

 the soil, but never became wet, and kept both weevils and squares 

 clean, besides facilitating the handling necessary to frequent renew- 

 als of the food supply and the consequent transference of the weevils. 

 The rest of the cage was formed by an ordinary lantern globe cov- 

 ered at the top by cheese cloth held firmly in place by a rubber band. 

 With this apparatus weevils could be readily observed without dis- 

 turbing them, and food supplied was kept in good condition and could 

 be easily renewed, while there were no cracks to hide in or to allow 

 weevils to escape (PL IV, fig. 23). The moisture of the soil and 

 fresh leaf covers were renewed as needed. Clean squares were sup- 

 plied each day, and the actual number of egg and feeding punctures 

 recorded upon numbered slips kept with each cage. The sex of each 

 weevil was also determined and noted upon its death, thus giving an 

 accurate record of the number and sex of weevils responsible for the 

 punctures recorded. Most of the weevils used were bred, so that the 

 exact length of their lives is known. Length of life refers only to 

 adult life from the time of emergence from the square or boll to the 

 death of the weevil. Many weevils brought in from the field were 

 under observation in the laboratory for periods sufficiently long to 

 justify the inclusion of the results obtained from them with those of 

 weevils which were bred. Obviously the time these were under 

 observation does not represent their true length of life; therefore the 

 inclusion of both results renders the averages obtained the more con- 

 servative. 



21739— No. 45—04 3 



