Chapter I 

 INTRODUCTION 



For the purpose of studying inheritance, the 

 Insects have been of primary importance, chief- 

 ly because their life cycle is short, and be- 

 cause they produce large numbers of progeny. 

 The fruit-fly, Drosophila melanogaster, and the 

 bee, Apis mellifica, have been studied inten- 

 sively by a number of workers; but the parasit- 

 ic wasp, Habrobracon juglandis (Ashmead), has 

 been given special study by P. W. V/hiting and 

 his co-workers during the past thirty years. 



Habrobracon is a parasitic hymenopteran of 

 the superfamily Ichneumonoidea, family Braconi- 

 dae, subfamily Vipiinae, genus Microbracon, 

 species hebetor (Say) (Muesebeck, 1925). The 

 species M. hebetor, was first described in 1836 

 by Say who, however, called it Bracon hebetor. 

 Later that same year he described another spe- 

 cies, which he called B. dorsator. The spe- 

 cies, B. hebetor and B. dorsator, are now known 

 to be the same. Many other names have been ap- 

 plied to this insect since the original ones 

 proposed by Say: B. brevicornis (Kirby, 1884; 

 Marshall, 1885), B. juglandis (Ashmead, 1889), 

 Habrobracon hebetor (Johnson, 1895), Bracon 

 (Habrobracon) honestor (Riley, 1895; Howard, 

 1895), Habrobracon benef icientior (Yiereck, 

 1911), H. brevicornis (Cushman, 1914; P. W. 



