NOTES ON INSECT BIONOMICS. 



BY V. L. KELLOGG AND R. G. BELL, STANFORD UNIVERSITY, 



CALIFORNIA. 



In connection with the experimental breeding and rearing under 

 controlled conditions of food supply of many lots of silkworms 

 {Boinbyx mori) during the last three years, the writers have made 

 certain observations and experiments incidental to the main object 

 of the investigation, the results of some of which may be here 

 briefly abstracted. 



Food Conditions in Relation to Sex Diferentiation. 



It has been assumed by some authors that poor nutrition of de- 

 veloping organisms is an extrinsic influence tending to determine 

 the sex of the organism to be male and good nutrition an influence 

 tending to produce females. The most important part of the as- 

 sumption is the idea that sex is subject to control by the environ- 

 ment of the organism — that sex is not inherently predetermined in 

 the germ. 



From the notes of the writers recording the results of an ex- 

 perimental rearing of numerous lots of silkworms on reduced ra- 

 tions in 1 901, 1902 and 1903, the following data are extracted 

 touching the problem of the relation of nutrition to sex differen- 

 tiation. From an inspection of these data it will be noted that a 

 test is included of the possible influence of poor nutrition of the 

 parents (and grandparents) in determining the sex character (if 

 predetermined) of the germ cells, as well as of the possible imme- 

 diate influence of nutrition in determining the sex of developing 

 individuals. It will be noted also that we have had in mind the 

 justly made criticism of most observations on the food and sex 

 problem, namely, that no attention is paid in records of an appar- 

 ent overproduction of males following poor nutrition, to the deaths 

 which ensue before the count is made, and that, as the females (it 

 being assumed) actually require more food to complete their de- 



