406 COTTON 



to some extent by the much lower temperature con- 

 ditions. These females were supplied with sugar-syrup 

 for food. The table on p. 405 shows the egg-laying record 

 and life of each female. These figures are not of very 

 great value, as they only deal with a limited number of 

 individuals, and have not been duplicated or carried out 

 under more normal surroundings. However, they show 

 that the females will breed and oviposit at a temperature 

 ranging from 50 to 60 F., also that under certain con- 

 ditions the egg-laying period may extend in a somewhat 

 irregular fashion over a considerable number of days, and 

 that the life of a female may last well over a month. 



How these results would compare with what actually 

 takes place in the field it is not yet possible to say. 



The fact that larvae in all stages of growth, eggs, 

 pupae, and adults, may be found in the same field and at 

 the same time throughout the summer months tends to 

 show that possibly the egg-laying period may last some 

 little time. 



Incubation Period and Hatching of the Egg. During 

 the summer months the egg stage lasts from three to 

 four days, but in late autumn and winter it will be 

 extended to eleven or twelve days. 



A short time before hatching the egg becomes dark 

 in colour owing to the head of the larva showing through 

 the shell. 



When ready to emerge from the egg the young boll 

 worm bites vigorously at the shell until it makes a hole 

 through it, generally at the base of the primary crown. 

 The hole is gradually enlarged until it permits of the 

 easy passage of the head. This having been accom- 

 plished, the larva crawls out free of the shell. The 

 process of eating a passage through the shell is not con- 

 tinuous, rests being taken at intervals; the young cater- 

 pillar appears to find it hard work to bite through the 

 main vertical ribs. The period occupied from the time 

 the boll worm first commences to bite at the shell until 

 it finally escapes varies in length; sometimes it only 

 takes about twenty minutes, at others it may be pro- 

 longed to fifty minutes. 



The empty egg-shell is dull transparent white, and 



