74 THE MEXICAN COTTON-BOLL WEEVIL. 



included 197 specimens, 23 larvae, 30 pupa?, and 144 adults. It is 

 therefore evident that large numbers of weevils go into the winter 

 in the immature stages, and there is every probability that, in the 

 southern part of Texas at least, many of them live and mature, 

 emerging m the spring. It may be that this gradual maturity of the 

 hibernated weevils is one of the reasons why they emerge so irregu- 

 larly from their winter quarters. 



Prof. Sanderson, in Bulletin 63 of the Bureau of Entomology, 

 mentions that in March, 1903, Mr. W. P. Allgood sent aim from 

 Devine, Medina County ,Tex., a quantity of bolls, which were examined 

 March 12. Twenty per cent of the bolls contained weevils, alive or 

 dead, in some stage. In 40 bolls there were 40 live and 11 dead 

 pupse, 30 live and 40 dead adults, and 5 dead larva?. Many of the 

 adults had just transformed from pupae. One live larva was found 

 in the material. Estimating the survival of weevils in the plants in 

 this field, Prof. Sanderson calculated that there would be about 10,500 

 weevils per acre in the spring. The lowest temperature which the 

 weevils experienced in the locality from which these bolls were sent 

 was 23° F. in February. 



SEASONAL ABUNDANCE. 

 BROODS OR GENERATIONS. 1 



The term "brood" can hardly be applied in its usual sense to the 

 generations of the weevil, as was pointed out by Dr. L. O. Howard in 

 the first circulars of the bureau dealing with the problem. For 

 several reasons no line of distinction can be drawn between the genera- 

 tions in the field at any season of the year, not even between hiber- 

 nated weevils and the adults of the first generation. As has been 

 shown, the period of oviposition among hibernated females is in some 

 cases fully 3 months, while it averages 48 days. The average 

 period of the full life cycle for the first generation is 25 days, and as 

 the time for the second generation would be slightly less, it is evident 

 that the first eggs for the third generation may be deposited at the 

 same time as those for the middle of the second generation, and also 

 with the very last of the eggs deposited by hibernated females for the 

 first generation, as shown in figure 14. The great overlapping of 

 generations thus produced prohibits the application of any of the 

 common methods of ascertaining their limits. The complexity 

 indicated for the first three generations becomes still further increased 

 as the season advances, so that in October, for example, a weevil 

 taken in the field might possibly belong to any one of five or six 

 generations. Duration of life and the period of reproductive activity 

 are important factors in determining the average number of genera- 

 tions. Periods of greatest abundance can not be regarded as giving 

 any reliable information upon this point, since the number of weevils 

 developed soon comes to depend largely upon the supply of squares. 



In tiie case of the boll weevil, therefore, the information upon the 

 number of generations must be drawn mainly from laboratory sources, 

 but the results are supported by observations made in the field. Many 

 of the hibernated weevils continue to deposit eggs until the middle of 

 July, and some are active for fully a month longer. In 1903 the last 

 eggs from hibernated weevils were deposited on August 27. In the 

 course of rearing experiments made in 1902 it was found that many 



* The following two paragraphs are taken from Bull. 51, Bureau of Entomology, pp. 95, 96. 



