578 SIDNEY I. KORNHAUSER 
tics. Since the head, thorax, and abdomen of parasitized males 
show such a decided change toward the female condition, it was 
of course puzzling to understand why the genital appendages 
showed not the slightest tendency toward such a transformation. 
A study of the structure of the adult gonapophyses of both sexes 
and their mode of origin was undertaken. The results of this 
study not only justify the classification of sexual characteristics 
used in this paper, but also show why the two categories of 
secondary sexual characteristics behave differently under the 
effects of parasitism. 
The external genitalia consist of three pairs of appendages in 
both sexes. In the male they are terminal, located on the last 
complete abdominal segment, the ninth. In the female they 
are produced cephalad on the ventral surface, reaching into the 
indentation of the seventh sternum. They are, however, con- 
nected entirely with the sclerites of the eighth and ninth ab- 
dominal somites.? 
The male genitalia (figs. 24 and 25) consist of a pair of ventral 
valves, a pair of styles or claspers, and an unpaired oedagus. 
The ventral valves (fig. 24, v.) are flattened sclerites united in 
the median plane for more than half their length, and produced 
caudad into a pair of free, narrow appendages, composed of two 
layers of chitinous cuticula closely approximated and envelop- 
ing the hypodermis which produced them. ‘The claspers are 
strong chitinous rods, each produced into a hook laterad to the 
oedagus (figs. 24 and 25, cl.). Each articulates with the side of 
the heart-shaped sternum of the ninth segment and extends 
2 The terms used in reference to the genital appendages are merely descrip- 
tive and bear no phylogenetic implications. From a study of a more primitive 
homopteran, such as the ordinary Cicada linnei Grossb., one may see that the 
gonapophyses originally arose from the eighth, ninth, and tenth abdominal 
somites. This is very clearly seen in the female, although a trifle obscured in 
the male, where the appendages are so modified and specialized that they are of 
great use to the systematist in a study of the Cicadidae. It is the writer’s belief 
that in the membracids the gonapophyses originated from the primitive eighth, 
ninth, and tenth abdominal appendages, even though in the male they all seem 
to arise from the ninth segment. A careful study of the embryonic stages might 
reveal a migration and persistence of the cells of the limb buds of the segments in 
question. 
