64 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 



The diversity in size of the boll weevil-, while not unprecedented 

 among insects, is unusual, and not without biological significance in 

 the present connection. An explanation of the variation in size i> 

 to be found, no doubt, in the varying amounts of food which the 

 weevil larvae can obtain, but there i> needed, none the less, a special 

 adaptability on the part of the weevil to permit it to reach a normal 

 reproductive maturity in spite of very unfavorable conditions. The 

 smaller weevils probably have les> than a quarter of the weight of 

 the large ones, which means that they are able to develop with a cor- 

 respondingly small proportion of the food required to raise a full- 

 sized weevil. The weevil- developed in the bolls have a much greater 

 uniformity of >ize. The -mall weevils are at once a means and a 

 result of the acquisition of the habit of living in the buds, and espe- 

 cially in the small one-, where the supply of food is often very small. 



RELATION BETWEEN PROLIFERATION IN BUDS AND IN BOLLS. 



The analogy of the mucilaginous tissue found in the young fruits 

 of okra and other relatives of the cotton would lead us to expect that 

 proliferation could occur more readily in the boll than in the bud. 

 which may mean that all the varieties which proliferate in the bud 

 will do so in the bolls as well. 



It was at first supposed that if the buds proliferated but not the 

 bolls the result would be merely a postponement of the breeding 

 season of the weevil for two or three weeks, or until the bolls had time 

 to develop. Such a delay would be of great practical importance in 

 retarding for that length of time the effective breeding period of the 

 weevils. Moreover, most of the eggs of the weevils which had passed 

 through hibernation would be lost by being laid in the buds, which 

 would further keep down numbers in the early part of the season. 

 There is. however, the further and still more important consideration, 

 that the period of development of the weevil in the boll is very much 

 longer than required for it to mature and emerge from the >quare.' 7 



o Determinations of the length of the life cycle in bolls have been made only 

 in a few instances. In 7 cases between August 15 and November 11. 1903. 

 the average time required from the deposition of the egg to the escape of the 

 adult from the opening boll was sixty-one days. The average effective tempera- 

 ture for the period was 31.7° F.. and the average total effective temperature 

 required for development in bolls was therefore 1.933.7° F.. or nearly two aud 

 one-half times as much as in squares. Several larvae often develop within a 

 single boll. They appear to remain in the larval stage until the boll becomes 

 sufficiently mature or so severely injured as to begin to dry and crack open. 

 When this condition of the boll is reached, pupation takes place, and by the 

 time the spreading of the carpels is sufficient to permit the escape of the weevils 

 they have become adult. — Hunter. W. D.. and Hinds. W. E.. The Mexican Cotton 

 Boll Weevil. Bui. 45. Division of Entomology. U. S. Dept. of Agriculture. 1904. 

 p. 75. 



