Chapter VI 



SEX CONDITIONS 



Like other hymenopterans , Habrobracon juglan- 

 dis is parthenogenetic in that males are pro- 

 duced from unfertilized eggs, so that the males 

 possess only a single set of chromosomes. Fe- 

 males which normally develop only from ferti- 

 lized eggs have a double set of chromosomes and 

 are diploid. The haploid males are extremely 

 useful in genetic studies, since their appear- 

 ance indicates their exact genetic composition. 

 The females, being diploid, may bear more fac- 

 tors than they show, since the effects of cer- 

 tain genes may mask those of others, which are 

 recessive. In order to bring recessive alleles 

 to light, females are set unmated on Ephestia 

 caterpillars and allowed to lay eggs. The re- 

 sulting sons exhibit the effects of all the 

 genes carried by their mothers, since during egg 

 maturation the paired chromosomes of the fe- 

 males separate giving dominant genes to some 

 eggs and their recessive alleles to others. For 

 this reason, the wasp is an especially advanta- 

 geous animal for genetic studies, since in one 

 generation only, all of the genie characters 

 possessed by the stock are brought to light. 



Occasionally females from unfertilized eggs 

 (thelytoky) are found in fraternities which nor- 

 mally produce males from unfertilized eggs 



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