172 Annals Entomological Society of America [Vol.1, 



of striking form and coloration, of which there was a single male. 

 The parents, which were collected in July, 1903, near McPherson, 

 Kansas, were sent to Chicago and reared in a second generation 

 which was normal; they hibernated until May, 1904, and then 

 emerged, reproduced, and among the progeny was this single male 

 rubrivittata. This male was crossed with a female decemlineata 

 from Chicago, and gave a hybrid brood intermediate in character 

 between the parents. Three males and one female of this lot 

 escaped the general extermination of my experiments in July, and 

 were carried over into 1905, giving after transfer to Mexico in 

 March, 1905, a Mendelian splitting into typical rubrivittata and 

 hybrid forms (text — fig. 22). These were separated and reared. 

 The pure cultures of rubrivittata showed as a result a new charac- 

 ter, namely, that its life-history as well as less important charac- 

 ters were changed, there being three generations in its yearly 

 cycle instead of two, as in the parent species, and in all of the 

 species in its immediate ancestry. 



"This change in the life cycle from hibernating in every 

 second generation, as do most of the species in the genus, to hiber- 

 nating in every third, is striking and significant, the three genera- 

 tions being gone through in about the same time as the two of the 

 parent species. The cultures with rubrivittata demonstrate 

 clearly that changes in physiological characters can take place 

 rapidly, as do changes in structure, and that these changes may 

 alter not only unimportant characters, but most fundamental ones 

 as well. We shall have occasion to consider a similar case even 

 more striking and interesting in a later portion of this chapter." 



The remaining case referred to in the last sentence of the 

 quotation just ended (from pp. 280-281) is now given for conven- 

 ience and in order to place all of them as near together as possible ; 

 space does not allow of its being given in full, and I give a brief 

 history of it until the variation appears. Beetles emerging from 

 hibernation in May, 1901, (Tower, lb., p. 288) were reared until 

 May, 1902, under normal conditions without extreme variation. 

 They were then divided into two lots and subjected, one to hot 

 and dry conditions, and the other to hot, dry and low pressure 

 conditions. The first is considered.* 



"From the apparently pure stock, 7 males and 7 females were 

 in May, 1902, subjected during the first half of their reproductive 



*The other lot appears to have been ignored, though a statement is made 

 to contrary (p. 288). 



