SEX DIFFERENTIATION IN LARVAL INSECTS. 



VERNON L. KELLOGG, 



STANFORD UNIVERSITY, CALIFORNIA. 



The question of the causes of sex differentiation is a problem 

 to the solution of which we seem now to be only a little nearer, 

 despite numerous researches, than we were many years ago. It 

 is advisable, perhaps, to continue to attempt to overcome some 

 of the outworks of this well entrenched problem. One of the 

 outliers of the main problem may be described in the phrase 

 "When is sex differentiated?", another in the phrase "Does 

 nutrition affect sex ? " 



Being engaged in rearing experimentally large numbers of 

 silkworm moths, Bombyx mori, I have taken advantage of the 



FIG. I. Section through female Bombyx larva, just after the third moult ; //, heart ; 

 al. c, alimentary canal ; r. n. c, ventral nerve cord. 



opportunity to test for this species both these subsidiary parts of 

 the sex differentiation problem. Various lots of larvae were set 

 apart, each individual being isolated so as to insure identity of 

 nutrition conditions, and fed on short rations. The result of 

 these experiments is given in a paper in the Journal of Experi- 

 mental Zoology (vol. i, pp. 357-360, 1904). It is sufficient 



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