554 SIDNEY I. KORNHAUSER 
genetically into males. The offspring of a single egg, as tested 
in laboratory cultures, were all of the same sex. However, as 
noted by Patterson in Paracopidosomopsis (’17), both sexes may 
emerge from a single host, and this would not be impossible in 
the case of Aphelopus, for at times a female might oviposit in a 
nymph already containing an Aphelopus ovum. This was 
demonstrated in the laboratory and both eggs were recovered by 
dissection. Twice in parasitized Thelia secured in nature Aphe- 
lopus larvae of two distinct stages of development have been 
found in single individuals. In these cases only those coming 
from the first ovum would become adults, for the host would 
be killed at their emergence; but, should two ova be laid within 
a short time in the body of a Thelia, it would be possible that 
some offspring of both ova would reach maturity at the same 
time and produce a mixed brood. 
6. CHANGES INDUCED BY APHELOPUS IN THE COLOR AND FORM 
OF THE INTEGUMENT AND APPENDAGES OF THELIA 
A. The thorax 
In Thelia, as in most membracids, the pronotum forms a 
conspicuous part of the organism. It is continued forward and 
upward as a horn projecting beyond the head, and it also ex- 
tends caudad as the posterior process covering the dorsum of 
the entire thorax and abdomen. The pronotum constitutes one 
of the most conspicuous differentiating characteristics of the 
extragenital type between the sexes. In the male (fig. 5) it has a 
uniform, chocolate-brown color with a conspicuous orange- 
yellow vitta on each side, extending caudad from the humeral 
angle usually about half-way to the tip of the posterior process. 
The length and form of the pronotal horn as well as the angle it 
makes with the rest of the body are subject to the greatest vari- 
ation, as 1s shown in figure 7. Sometimes it is long, curved, 
slender, and erect, (7, d, 7, h); again, short, straight, and blunt 
(7,e, 7,1). The form of the vitta is also variable, the yellow 
color showing many degrees of extension toward the tip of the 
posterior process. Figure 7 is a series arranged from a to l to 
