Hahrobracon 501 



True gynanders appear occasionally in Habrobracon and consist 

 of part diploid female and part haploid male tissue. In some 

 eggs of this wasp, two haploid nuclei are present. If the female 

 is homozygous for any recessive gene, each nucleus will have one 

 of these genes. AVhen such a binucleate egg is fertilized, the 

 male nucleus unites with one of the two egg nuclei. If the male 

 bears the dominant allele of these recessive genes, the diploid 

 tissue which develops from the fertilized egg nucleus and will 

 form the female part of the gynander will show the dominant 

 character whereas the tissue which develops from the unfer- 

 tilized egg nucleus will be phenotypically recessive. Such gy- 

 nanders may have a head of one sex and an abdomen of the 

 other, one side of one sex and the other side of the opposite sex, 

 islands of male or female tissue in otherwise female or male 

 regions, or other combinations of male and female regions. When 

 the genitalia contain tissues of both types, there may be a full 

 set of male structures and a half set of female structures. 



Another type of gynander found in Habrobracon, although 

 infrequently, has haploid male parts which have developed andro- 

 genetically. Androgenesis means haploid development from a 

 sperm nucleus. Among fertilized eggs of this insect, about 1 per 

 cent are fertilized by two sperm. If one of the sperm nuclei can 

 develop without uniting with an egg nucleus, the tissue which 

 arises from it will be haploid and therefore male, but will be 

 androgenetic. Thus gynanders can be formed with some andro- 

 genetic tissue. 



Resembling gynanders in some respects are certain haploid 

 males called gynandroid. They develop from eggs which con- 

 tain two functional haploid nuclei, but are not fertilized. They 

 are mosaics of two types of tissue containing different sex alleles. 

 They are entirely male in appearance except that certain small 

 feminized structures are added to the male genitalia, usually on 

 one side. The theory of complementary genes explains such 

 situations admirably. If the female was xa / xb, one part of the 

 body would be xa and the other xb, and both would be male. 

 Where the two sections join, secretions from the xa region might 

 diffuse into the xb region for a short distance, and in these regions 

 of diffusion the complementary action of the two gene products 

 would produce some female structures. 



