SEASONAL HISTORY. 65 



PERCENTAGE OF EGGS THAT HATCH. 



Definite records have not been kept regarding the percentage of 

 eggs that hatch, but in the many hundreds of eggs followed during 

 these observations very few have failed to hatch. Though some are 

 nmch slower in embryonic development than are others laid at the same 

 time and by the same female, it is probable that less than 1 per cent 

 of the eggs are infertile or fail to hatch. It must be considered, 

 however, that proliferation crushes many eggs. This proliferation 

 is most aggressive against the eggs in the bolls in the late fall. 



THE LARVA. 

 FOOD HABITS. 1 



It is plainly the instinct of the mother weevil to deposit her egg so 

 that the larva upon hatching will find itself surrounded by an abun- 

 dance of favorable food. In the great majority of cases this food 

 consists principally of immature pollen. This is the first food of the 

 larva which develops in a square, and it must be both soft and 

 nutritious. Often a larva will eat its way entirely around the inside 

 of a square in its pursuit of this food. In most cases the larva is 

 about half grown before it feeds to any extent upon the other por- 

 tions of the square. It may then take the pistil and the central 

 portion of the ovary, scooping out a smoothly rounded cavity for the 

 accommodation of its rapidly increasing bulk. So rapidly does the 

 larva feed and grow that in rather less than a week it has devoured 

 two or three times the bulk of its own body when fully grown. It 

 sometimes happens that the square is large when the egg is depos- 

 ited therein, and the bloom begins to open before the injury done 

 by the larva becomes sufficient to arrest its development. In many 

 cases of this kind the larva works its way up into the corolla and 

 falls with it when it is shed, leaving the young boll quite untouched. 

 Occasionally the flower opens and fertilization is accomplished before 

 any injury is done the pistil, and in rare cases a perfect boll results 

 from an infested square. Sometimes the larva when small works its 

 way down into the ovary before the bloom falls, and in such cases 

 the small boll falls as would a square. (See PL VI, a, b, d.) 



In large bolls the larvae feed principally upon the seed and to 

 some extent upon the immature fiber, A larva will usually destroy 

 only one lock in a boll, though two are sometimes injured. When 

 the infestation is severe a number of weevils, occasionally as many 

 as six or even more, may be developed in a single boll, which is 

 completely destroyed by the feeding of the larvae. (See PL VII, a, c.) 



GROWTH. 



The rate of growth, of course, is dependent upon many external 

 conditions. It has been found that in squares during the hot weather, 

 the length of the body increases quite regularly by about 1 mm. a day. 

 Full grown larvae vary in length from 5 to 10 mm. across the tips of 

 the curve. Larvae of normal size in squares average from 6 to 7 mm. 

 The largest larvae are developed in bolls which grow to maturity. 



1 From Bulletin 51, Bureau of Entomology, p. 49. 



28873°— S. Doc. 305, 62-2 5 



