556 tHE ENTOMOLOGISt. 



prompted to forsake iheir food and prepare for the transfor- 

 mation by the changes ah'eady taking place in the system, 

 and in the great raajority of cases the raandibulate is ah'eady 

 giving way to the hauslellate mouth, and has become impo- 

 tent to perform its wonted labour. Larvae can neither be 

 forced nor stuffed beyond a certain limit, and this limit is 

 attained by every well-fed larva in a stale of nature and in the 

 vivarium, so that if Mrs. Treat's theory had any real founda- 

 tion, almost all insects that were not "starved" ought to be 

 females. A high temperature will cause rapid development, 

 but it does not cause a greater aggregate amount of feeding. 



But to my own experiments. Of the six insects chosen, the 

 sexes in some differ in the most remarkable manner, while all 

 show sufficient disparity to render mistakes in separating the 

 sexes impossible. They are, also, all common in this section, 

 so that others will have no difficulty in verifying ray facts. 

 Except in the case of Thyridopteryx I made no attempt to 

 "feed-up," my efforts all being in the direction of "starving," 

 or, as Mrs. Treat would put it, of producing males. Neither 

 have 1 relied entirely on my own observation; for, being 

 necessarily absent from home, at intervals, the experiments, 

 with explicit directions, were at such times left in charge of 

 Mr. Otto Lugger and Miss Mary E. Murtfeldt, both well 

 practised in rearing Lepidoptera. I would also premise that 

 the stunting process began from the time of hatching, and 

 that it was carried so far that, of the less hardy species, many 

 died under the treatment. It was, also, especially enforced 

 towards larval maturity. The species chosen were: — 1, Thy- 

 ridopteryx ephemeraeformis; 2, Orgyia leucostigma; 3, Cli- 

 siocampa Americana ; 4, Hyperchiria lo ; 5, Ilemileuca Maia ; 

 6, Anisola rubicunda. 



1. Thyridopteryx ephemercBformis. — Two lots : lot 1, con- 

 sisting at first of between thirty and forty individuals, and 

 abundantly and constantly nourished ; lot 2, of thirty indivi- 

 duals, and very poorly nourished, or " starved." From lot 1, 

 twenty-eight cocoons were obtained, of which fifteen were 

 males and thirteen females, all of them attaining the imago 

 state. From lot 2, eighteen cocoons were obtained, which 

 produced twelve males and six females, two of the females 

 failing to perfect, and dying in the chrysalis state, in which 

 the sex is readily determined. The stunted lot produced, on 



