582 SIDNEY I. KORNHAUSER 
Many descriptions of membracid nymphs have been written 
and a detailed account of the five nymphal instars of Thelia 
has recently been published (Funkhouser, ’15), but no mention 
is made of characteristics which may be used to distinguish the 
sexes. Neither in coloration, nor in the form of the integument, 
nor in the thoracic appendages is any clew given to the sex of 
the nymph. In the fifth instar the female abdomen is noticeably 
larger and wider than the male abdomen; but an infallible test 
for the sex of the nymph is to be found by examining the ventral 
surface of the eighth and ninth abdominal segments. The 
genitalia are so well developed in the nymphs and are so dis- 
tinctly different in male and female that, as early as the third 
instar, one can determine the sex by an examination of the ven- 
tral surface of the eighth and ninth somites with a hand lens. 
Figures 40, 41, and 42 show the form of the genitalia in male 
nymphs of the third, fourth, and fifth instars, respectively, 
whereas the corresponding stages in the female are shown in 
figures 44, 45, and 46. The sexes are easily recognizable, not 
only by the form and position of the appendages, but also by the 
pigmentation of the eighth sternum. 
Examining the characteristics of the three stages of the male 
represented in figures 40, 41, and 42, we find that the genitalia 
arise in a triangular-shaped area on the ninth abdominal seg- 
ment. Small chitinous pockets pointing cephalad contai then 
hypodermal cells which produce the genitalia. In each instar 
Fig. 40 Abdomen of male third nymphal instar, ventral view, caudal portion 
showing genital area (g. a.) and characteristic pigmentation of sternum of eighth 
somite (s. 8). XX 26.2. 
Fig. 41 Abdomen of male fourth nymphal instar, caudal segments, ventral 
view, showing inner (dorsal) pockets as smaller pair, and outer (ventral) pockets 
of genital area. Medial partition in each pair. X 26.2. 
Fig. 42 Abdomen of male fifth nymphal instar, ventral view of entire ab- 
domen. Inner pockets now three in number, median and two lateral; outer 
pockets still right and left of median partition. Pigment confined to ends of 
pockets and partitions. X 9.7. 
Fig. 43 Abdomen of parasitized male fifth nymphal instar, ventral view of 
entire abdomen, showing extreme reduction of inner pickets of genital area due 
to action of parasites. The holes in the sterna were made by escaping eruciform 
larvae, which left their exuviae (those of megagnathic stage) at puncture holes. 
x 9.7. 
