SEX INHERITANCE 117 



group of Lepidoptera has furnished more cases than 

 all others taken together, although gynanders have 

 been found also in bees, wasps, ants, and less fre- 

 quently in other groups of insects; also they occur 

 in spiders and lice, and rarely in Crustacea and other 

 groups of animals. It is seldom possible to discover 

 the causes of these gynanders, either because their 

 ancestry is unknown, or because the heredity of the 

 characters involved has not been worked out. In 

 Drosophila, on the other hand, over a hundred 

 gynanders have arisen in pedigreed cultures, in 

 which known hereditary characters were present; 

 and, in fact, in some cases the cultures had been 

 made up in such a way as to give critical evidence 

 as to the origin of the individuals. 



The most striking gynanders are those in which 

 one side of the body is female and the other side 

 male. The earliest of the completely bilateral 

 gynanders found in Drosophila is that shown in 

 c of Fig. 36 G. The right side of this fly was female 

 throughout, and the left side male. The left side 

 of head, thorax, and abdomen was smaller than the 

 right side, the antenna, the bristles, the legs, and 

 the wing of the left side were also smaller than the 

 same organs on the right side. Besides these differ- 

 ences in size, the left fore-leg bore a distinctly male 

 character, the sex-comb, and the left side of the 

 abdomen was colored and segmented as in the 

 male. The genitalia (in c, of Fig. 36, G) were 

 distinctly of the male type on tlie left side, but on 

 the right the structures are neither purely female 



