288 Annals Entomological Society of America [Vol. IV, 



females and from these 169 beetles were reared in the first 

 generation. All but one were either melano pleura or annectans 

 according to the composition of the female. This one excep- 

 tion was a humeralis beetle. A noticeable character of the 

 progeny of these crosses was the greater vigor of the individuals 

 so that a larger percent matured as compared with the purer 

 strains. From one of the above three pairs, an annectans 

 female and a humeralis male, the first generation of which con- 

 sisted of fifty-seven annectans, four second generation beetles 

 were reared and they proved to be two annectans and two 

 humeralis. The beetles then refused to lay any more eggs and 

 seemed to be preparing for hibernation. They had been 

 unavoidably subjected for a few days to a temperature low 

 enough to stiffen them up considerably and cause them to 

 nearly cease eating and the subsequent removal of them to an 

 almost summer temperature, though it caused the eggs to 

 hatch in half the time they had under the low temperature and 

 increased the appetites and rate of growth of the larvae quite 

 remarkably, failed to cause the beetles to lay any more eggs. 

 Work had, therefore, to close for the season at this interesting 

 point, and the beetles were put into hibernation.* 



From these crosses there is another lesson to be learned 

 besides the relation of annectans and melanopleura to humeralis, 

 namely; something about the heredity between melanopleura 

 and annectans themselves. The process of mating these forms 

 with humeralis which is recessive to both, served as a test of the 

 germinal composition of the member of the pair carrying the 

 dominant characters. In the case where two melanopleura 

 females, which had been isolated from annectans from time of 

 emerging were crossed with humeralis males there were pro- 

 duced 29 melanopleura to 2.") annectans, and 31 melanopleura to 

 26 annectans respectively. Melanopleura was in each case a 

 little in excess of 50 percent. In the case of the annectans- 

 humeralis hybrid female mated with the melanopleura-annec- 

 lans male the progeny was 10 melanopleura and 28 annectans. 

 The higher percent of annectans was doubtless due to the fact 

 that an annectans male was put into the cage during the latter 



* Just as this article was ready to send to the publisher a lot of second genera- 

 tion beetles, from the melanopleura females crossed with the humeralis males, 

 emerged. From the eggs of the first generation melanoplenra-humeralis hybrids 

 there were reared 19 melanopleura and 7 humeralis. From the eggs of the first 

 generation armectans-humeralis hybrids there matured 12 annectans and .5 humeralis 

 These figures come very near to the Mendelian ratio for progeny of hybrids. 



