SEXUAL CHARACTERISTICS OF THELIA 575 
show these rows to be on the average 7.5u apart. In the females 
these rows arch cephalad on the sterna and are 9.34 apart on 
the average. In parasitized males, instead of forming straight 
lines, they are curved as in the female and are 9.5 apart. 
These changes in the arrangements of the minute spines of 
male abdomens may not be ascribed to the retention of juvenal 
characteristics, for the integument of the fifth nymphal instar of 
both sexes is quite different from that of the adult. The terga 
of the nymph are covered with large jointed hairs (fig. 18, p. 562) 
and lack entirely the minute hairs arranged in patterns in adult 
terga. Also the nymphal sterna are clothed with peculiar 
triangular spines quite unlike those of the adult and not arranged 
in definite rows. 
The sclerites of the eighth and ninth abdominal segments and 
the sterna of the seventh segment are quite dissimilar in the 
two sexes, being modified in each sex to accommodate the gona- 
pophyses. Thus the sterna of the seventh and eighth abdominal 
somites are rectangular in the male (figs. 24 and 25, s. 7, s. 8), 
not unlike those more anterior. The sternum of the ninth 
segment of the male abdomen is a single small heart-shaped 
sclerite (fig. 24, s. 9), which articulates laterad with the claspers 
and caudad at its apex with the oedagus. In the female the 
immense ovipositor extends so far cephalad that the sternum of 
the seventh somite (fig. 28, s. 7) is deeply indented, its caudal 
border forming an are cephalad which almost divides the sternum 
into two plates at its median plane. The sternum of the eighth 
somite in the female (fig. 28, s. 8) is represented by two laterally 
situated plates, each articulating with a gonapophysis of the 
pair belonging to that somite (fig. 28, gn. 8). In the ninth 
somite also the sternum is divided into two parts, each having 
the outline of a Roman lamp. Each of these plates (fig. 28, 
s.9) is covered by the pleuron of its respective side and has 
articulations with two gonapophyses (gn. 9 and gn. 9’), one at 
its cephalic end and one at its caudal end. 
In parasitized males, although the genitalia are not produced 
cephalad, the sternum of the eighth somite is often almost divided 
into two plates by a deep notch from its caudal border (fig. 27, 
