360 Venion L. Kellogg and R. G. Bell. 



The writers present these figures, actual data, for what they 

 may be worth. Like the data of the smaller lots previously re- 

 ferred to, they at least show that individuals living through their 

 whole post-embryonic life on the smallest food supply capable of 

 sustaining life, a supply varying from M to >^ of the supply nor- 

 mally used by individuals of the species, do not necessarily become 

 males. Whether the figures indicate an appreciable influence of 

 this nutrition on the determination of sex can be determined by the 

 readers as well as by the writers. In the rearing season (March 

 to June) of this year ( 1904), the writers purpose devoting much 

 larger lots of individuals to the continuation of the experiment. 



Forced Pupation. 



Experiments were made to determine how early in larval life 

 the food supply could be cut off without stopping the metamor- 

 phosis (development) of the silkworm, whether such forced ab- 

 breviation of the food-taking period results in any unusual struc- 

 tural or physiological modification in the stages which follow the 

 withdrawal of food, and whether the metamorphosis (in particu- 

 lar, pupation) is hastened when food is withdrawn in late larval 

 life, an adaptation often assumed to be possessed by Lepidoptera. 

 Such an adaptation would obviously be of real advantage, as it 

 might often save individuals from death due to a sudden disap- 

 pearance of the food supply, or to a sudden accidental incapacity 

 to gain access to the food supply. 



The silkworm spends normally about sixty days in the larval 

 (feeding) stage, divided into five actively feeding intermoulting 

 periods of about ten days each, by four brief two-day moulting 

 periods, during which no food is taken. On the eleventh or 

 twelfth day (from 270 to 300 hours) after the fourth moult, the 

 larva "spins up" and pupates. 



Twenty healthy silkworms were selected at random from a 

 large lot (several hundred) which had been reared in one tray, 

 all the individuals, of course, under the same condition of food 

 supply, temperature, humidity, light, etc. Of the twenty, one 

 was fed as long as it would take food; the other nineteen were de- 



