32 Journal New York Entomological Society. [vol vi„ 



larvae upon which these studies are based were kept in the insectary,. 

 and in a temperature varying probably from 6o° to 75 ° Fah. 



The species is a grass as well as a clover insect, as will be observed 

 from the foregoing, and as the striped body of the larvae would indicate, 

 but it would seem that the clover leaf is especially desirable as material 

 for constructing the cocoon, and it is just possible that the lack of this- 

 building material would account for the great variation in tastes in select- 

 ing such as was at hand to supply the place of clover leaves, thus the 

 better illustrating natural selection. 



The variation in rapidity of growth I am totally unable to account 

 for, as there was an abundance of food, and the larvae were never 

 crowded. With the individual variation in size and time required for 

 development in the larvae, as well as their difference in coloration, to- 

 gether with the equally striking difference in the appearance of the 

 adult, it would seem that in this case at least individual variation offered 

 no very narrow basis for the evolution of forms, which, under a favor- 

 able environment, might still further progress through varieties to species. 

 That this may have actually transpired, is witnessed by the exceedingly 

 close resemblance between Drasteria erechtea Cram, and D. crassiiiscula 

 Haw., either one of which might have given origin to the other, through 

 the same course of evolution as that, seemingly, being followed at pres- 

 ent by varieties agricola G. & R., ochrea Grt. , and distincta Neum., the 

 two latter being considered by Mr. Slingerland as varieties of D. crassi- 

 uscula. It only requires that these varieties become sterile to each other 

 and the parent stock when crossed, in order for them to become species, 

 as valid as either of the two just mentioned. 



Explanation of Plates IV and V. 



Fig. 1. Drasteria erechtea and cocoon. 

 <( o " " " " 



1; -, it (C « (' 



(( A H « (' » 



M r i( << « " 



« 6_ <( « « » 



" 7- Eggs, enlarged (pi. IV). 

 " 8. Larva, enlarged (pi. V). 



