37 



During the heat of summer the larval stage requires approximately 

 one week. This time appears to hold so long as the mean average 

 temperature remains above 75° F. As the temperature falls below 

 that point there is a gradual increase in the duration of this stage. 

 The average total effective temperature required during hot weather 

 by the larval stage is not far from 280° F. As development becomes 

 retarded by colder weather the average total effective temperature 

 required to complete it is much greater. 



These facts may be expressed in general by stating that during the 

 hottest summer weather the duration of this stage is somewhat less 

 than one week. Development becomes slower as the temperature 

 falls, but does not cease altogether so long as cotton can live. Even 

 moderate frosts do not destroy larvae in the squares and bolls, and 

 these ma} 7 finish development during warmer weather after the frost 

 has taken place. Hard frosts appear to kill both larvae and pupae in 

 squares and bolls. 



The duration of the larval stage in bolls is as a rule much greater. 

 If the boll falls when small the increase is slight, but if an infested 

 boll grows on to maturity the larval stage more than any other, is 

 much extended. Special observations upon the larval stage in bolls 

 have not been made, but reckoning from the known duration of the 

 whole developmental period in maturing bolls we may conclude that 

 the larval stage may frequently extend over six or seven weeks. 



PUPAL CELLS IN BOLLS. 



As the boll approaches maturity, the full-grown larva ceases to feed 

 upon the drying and hardening tissues of seed and fiber. Its excre- 

 ment, more or less mixed with lint, becomes firmly compacted, and in 

 the drying which occurs the mass forms a cell of considerable firm- 

 ness, within which pupation and the subsequent transformation to the 

 adult take place (PI. IV, rig. 14). These pupal cells frequently include 

 a portion of the hull of a seed, but the writer has never found a large 

 larva or a pupa entirely inclosed within a single cotton seed. The 

 cells described are shorter and thicker than seeds, but in general 

 appearance there is considerable resemblance between them (PI. IV, 

 fig. 17). Doubtless these cells have misled some into the statement 

 that they have found weevils in cotton seeds. 



PUPATION. 



The formation of the adult appendages has gone a good way before 

 the last larval skin is cast. The w ing pads appear to be nearly half 

 their ultimate size. The formation of the legs is also distinctly 

 marked, and the old head shield appears to be pushed down upon the 

 ventral side of the thorax by the gradual elongation of the developing 

 proboscis. Finally the tension becomes so great that the tightly 



