STUDIES ON THE PARASITIC WASP, HADRO- 

 BRACON BREVICORNIS (WESMAEL). 



II. A LETHAL FACTOR LINKED WITH ORANGE. 

 p. w. WHITING, 



ST. STEPHEN'S COLLEGE, ANNANDALE-ON-HUDSON, N. Y. 



Linkage of genetic factors has been demonstrated in many 

 widely diverse species of plants and animals. In animals it may 

 be complete in either sex, partial in the other; or it may be 

 partial in both sexes. In plants it is apparently partial in both 

 types of sporogenesis. Up to the present time linkage has not 

 been demonstrated in Hymenoptera. In species which produce 

 males by haploid parthenogenesis we might expect linkage in 

 ovogenesis to be partial. In spermatogenesis linked factors 

 would, of course, be completely linked as in the case of sex- 

 linked factors in Drosophila. Unlike sex-linkage, however, there 

 would be several independently segregating sex-linkoid groups, 

 corresponding to the reduced number of chromosomes. 



In the parasitic wasp, Hadrobracon, orange eye color is in- 

 herited as a sex-linkoid recessive to typical black. Heterozygous 

 females produce black and orange males in equal numbers as 

 previously shown. 1 



Three heterozygous sisters were isolated in July, 1920. One, 

 a virgin, produced 38 black males and 44 orange males. 



The second was bred as a virgin and later mated to one of her 

 orange-eyed impaternate sons so that females were produced. 

 Her progeny consisted of 57 black males, 44 orange males, 37 

 black females and 29 orange females. One of her black daughters 

 isolated as a virgin produced 14 black males and 16 orange males. 



Under normal conditions full-grown larvse of the wasp spin 

 cocoons before pupating which serve to attach them firmly in 



1 Whiting, P. W., "Studies on the parasitic wasp, Hadrobracon brevicornis 

 (Wesmael) I., Genetics of an Orange-eyed Mutation and the Production of 

 Mosaic Males from Fertilized Eggs," BIOLOGICAL BULLETII-J, Vol. XLI., No. i. 



153 



