. 



DESCRIPTION. 33 



becomes completed. These immature stages require on the average 

 between two and three weeks. A further period of feeding equal to 

 about one- third of the preceding developmental period is required to 

 perfect sexual maturity so that reproduction may begin. 



DESCRIPTION. 



THE EGG. 1 



The egg of the boll weevil is an unfamiliar object even to many 

 who are thoroughly familiar with the succeeding stages of the insect. 

 If laid upon the exterior of either square or boll, it would be fairly 

 conspicuous on account of its pearly white color. Measurements 

 show that it is, on the average, about 0.8 mm. long by 0.5 mm. wide. 

 Its form is regularly elliptical, but both form and size vary somewhat. 

 Some eggs are considerably longer and more slender than the average, 

 while others are ovoid in shape. The shape may be influenced by 

 varying conditions of pressure in deposition and the shape of the 

 cavity in which it is placed. The soft and delicate membrane form- 

 ing the outer covering of the egg shows no noticeable markings, but 

 is quite tough and allows a considerable change in form. Were the 

 eggs deposited externally they would doubtless prove attractive to 

 some egg parasite as well as to many predatory insect enemies. 

 Furthermore, the density of the membranes would be insufficient to 

 protect the egg from rapid drying or the effects of sudden changes in 

 temperature. All these dangers the female weevil avoids by placing 

 the eggs deeply within the tissue of the squares or bolls upon which 

 she feeds. As a rule, the cavities which receive eggs are especially 

 prepared therefor and not primarily for obtaining food. Buried 

 among the immature anthers of a square or on the inner side of one 

 carpel of a boll, as they frequently are, weevil eggs become very in- 

 conspicuous objects and are found only after careful search. 



THE LARVA. 2 

 (PI. Ill, a, b, c, e.) 



The young larva, upon hatching from the egg, is a delicate, white, 

 legless grub of about 1 mm. ( 2 \ inch) in length. Except for the 

 brown head and dark brown mandibles the young larva is at first as 

 inconspicuous as the egg from which it came. As it feeds and grows 

 it continues to enlarge a place for itself in the square or boll until the 

 food supply has become exhausted or the vegetable tissues are so 

 changed as to be unsuitable for food. By this time, as a rule, the 

 interior of the square has been almost entirely consumed and the 

 larval castings are spread thickly over the walls of the cavity. This 

 layer becomes firmly compacted by the frequent turning of the larva 

 as it nears the end of this stage. In the cell thus formed occur the 

 marked changes from the legless grub to the fully formed and perfect 

 beetle. 



Throughout this stage the body of the larva preserves a ventrally 

 curved, crescentic form. The color is white, modified somewhat by 



i Extract from Bulletin 51, Bureau of Entomology, p. 31. 



2 Extract from Bulletin 51, Bureau of Entomology, pp. 34, 35, 



28873°— S. Doc. 305, 62-2 -3 



