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 (nm c, of Fig. 36, G) were 
distinctly of the male type on the left side, but on 
the right the structures are neither purely female 
