146 THE CANADIAN ENTOMOLOGIST. 



of food was very irregularly given and short in quantity, yet the moths 

 produced from them consisted of four males, full sized, and eleven 

 females, some of these latter being much below the average of the species 



m size." 



I presume that the reason Mr. Fletcher supposed that the result may 

 have been very different was because he had read in " Newman " the 

 result of an experiment performed by an American lady, I think Mrs. 

 Treat, who, having underfed a lot of larv?e, succeeded in producing all 

 males, the inference drawn being that males were simply underfed 

 females. I wrote some notes on this subject for " Newman," thinking 

 that Mrs. Treats paper had appeared originally in that publication. It 

 seems, however, that it did not, and I now reproduce the substance of 

 those notes here, as more likely to meet the eyes of all concerned. 



First, then, I would remark that this clearly is not Nature's method of 

 " controlling sex." If a batch of larvae, say of K antiopa, all feed on the 

 same elm, there will be produced both males and females, although the 

 feeding must be alike for all. But there is an excellent opportunity 

 afforded Mrs. Treat of testing the value of her theory, by the larva of 

 Thyreus Abbottil (Swains.) It is well known that the male larva of this 

 species is altogether different in color from that of the female, so the 

 sexes are easily distinguished. 



Now, if Mrs. Treat wul take the female larvae, and by underfeeding it 

 produce male imagmes, the thing will be more satisfactory. I am not 

 unaware that in Hymenoptera food is said to have a good deal to do with 

 the production of sex, but still Mrs. Treat's experiment cannot be con- 

 sidered as conclusive. 



Hasty generalization is a fault to which we are very liable, and 

 doubtless the ambition to discover a new law is very laudable. A case 

 of this nature occurs in your No. 5, vol. 6. In a paper appearing in that 

 number, Mr. Gentry, of Germantown, fancies he has discovered the law 

 which produces difference of color in caterpillars of the same species. 

 Now, to be of any value, this-law must be universal, and the facts of the 

 case do not show any such universality. Mr. Gentry thinks that the 

 difference in color and markings where this occurs is attributable to the 

 difference in the chemical constituents of the food plant at different 

 seasons of the vear. He selects as one instance the larva of Eacles 

 impei'ialis^ and gives, correctly enough, three varieties of color. But, 

 unfortunately, these varieties occur at one part of the season as well as at 



