THE GENETICS OF HABROBRACON JUGLANDIS ASHMEAD 



islands in male regions. When genitalia are 

 mixed in sax, there may be a full set of male 

 structures and a half set of female structures. 

 Two of these cases have been published (P. W. 

 Whiting and A. R. Whiting, 1927). Gynanders in- 

 dicate tlmt the various sexual reactions are 

 determined by the head rather than by the repro- 

 ductive organs of the animal. Those with male 

 heads and female abdom^ens react towards females 

 but are in lif f erent to caterpillars ; while those 

 with female heads and male abdomens pay no at- 

 tention to females but respond to caterpillars. 

 Gynanders v;ith mixed heads act in general either 

 like males or li^-^e females. Gynandromorphic be- 

 havior is not all as clear-cut as the head and 

 abdomen variations described above. Some show 

 momentary sex-reversal for one or more brief 

 periods of time, and therefore, behave sometimes 

 like females and sometimes like males. There 

 is also a bisexual type of individual which at- 

 tempts to sting caterpillars as well as to mate 

 with females; and there is also a type v/hich has 

 been termed "wires crossed." These individuals 

 attempt to mate with caterpillars and to sting 

 females. All these various irregularities of 

 behavior are thought to be caused by the mosaic 

 character of the. sensory and nervous systems 

 rather than to any hormonal action. 



Very little evidence of intersexuality has 

 been found in Habrobracon so far. One mutant 

 type, gynoid, has been found, the gene for which 

 causes haploid males to be weakly intersexual. 

 Gynoid females are indistinguishable from wild- 

 type. The trait acts as a recessive in hetero- 

 zygous diploid males. Gynoid males are similar 

 to normal males in internal structure and in 



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