SEASONAL HISTORY. 



73 



Table XXVIII. — Table showing variations in (he developmental period of boll weevils 

 in the third generation at Alexandria, La., in 1907 — Continued. 



TOTALS AND AVERAGES. 



DEVELOPMENT OF WEEVILS IN THE SQUARES WHICH NEVER FALL. 



It is generally true that squares seriously injured by the weevil 

 sooner or later fall to the ground. The form of the absciss-layer 

 grown when the square is injured determines whether it is to fall 

 or to hang. (See PI. XV.) This will be explained fully in connec- 

 tion with the discussion of parasites (pp. 143, 144). 



Certain climatic and cultural conditions seem to increase the 

 tendency of the cotton plants to retain the infested squares, although 

 this tendency seems to be very largely of a varietal character. In the 

 hanging position the square dries thoroughly and becomes of a dark- 

 brown color. Although exposed to complete drying and the direct 

 rays of the sun, the larva 1 within are not destroyed by the sun in the 

 same proportion as those which are exposed to the sun on the hot 

 soil. However, control b\ r parasites is much greater in the hanging 

 squares than in the fallen squares — so much greater at times that the 

 total mortality from all causes in hanging squares surpasses that of 

 fallen squares. This matter will be dealt with more fully in a later 

 section. 



Owing to the much smaller number of squares which hang on 

 the plants, we have been unable to obtain a sufficiently large series 

 of records upon the development of the weevil in this class of squares, 

 but the records available show that the development is slightly 

 shorter in hanging squares than in the average fallen squares. 



DEVELOPMENT DURING WINTER, 



As is normal with many species of weevils, there is some develop- 

 ment during the winter months. This development, however, is 

 frequently cut short by severe freezes. In southern Texas larvae and 

 pupa? of the boll weevil which are in squares when frost comes are 

 not always killed thereby, but slowly finish their development if the 

 weather is warm enough for any activity, and the adults thus devel- 

 oped may live through the winter without feeding. Mr. J. D. Mitchell 

 took a number of live larva 1 , pupa?, and adults from bolls in a field at 

 Victoria, Tex., on December 26, 1903, after two hard frosts and one 

 freeze. Two weeks later, from a field in the same locality, after 

 three hard frosts and two freezes (30° F.), he took another lot of 

 live specimens in these three stages. On February 7, 1904, Mr. 

 Mitchell took 32 adults, 1 pupa, and 4 larva 1 , all alive, from standing 

 stalks, and on February 14 he found 32 adults, 2 pupa?, and no 

 larvae. The material collected at different times up to February 14 



