632 SIDNEY I. KORNHAUSER 
14. Male membracids show a greater degree of variation than 
do females. Males seem to have a less stable constitution and 
have departed from generalized types farther than have females. 
This difference in constitution probably rests on the chromatic 
makeup of the two sexes—the xx condition being more stable 
than the xy or xo condition. The male of Thelia bimaculata 
shows extreme departures from the female in many character- 
istics of form, size, color, and pattern. The male extragenital 
sexual characteristics and the specific characteristics of the 
gonapophyses first appear in the final molt. The extragenital 
sexual characteristics may be due to genes which in many cases 
modify characteristics once common to both sexes, but now 
exhibited in a primitive condition only in the more stable female. 
The metabolism of the parasites, altering the constitution of the 
host’s haemolymph which bathes the developing cells, may offer 
an environment unsuitable for these recent genes to find their 
expression and leave the male individual in a more primitive 
state exhibiting characteristics now found in the female of the 
species. 
Evanston, Illinois, 
May, 1918 
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