SEXUAL CHARACTERISTICS OF THELIA 577 
In parasitized females (figs. 30 and 31, t. 9, p. 9) no qualitative 
change occurs; the tergum remains practically normal and the 
pleura decrease in length, accommodating themselves to the 
shortened gonapophyses. 
Summing up the changes in the extragenital abdominal char- 
acteristics in parasitized males, we find that the abdomen in- 
creases in size; that the pleura become flat and ventral in posi- 
tion and in cross-section the abdomen is similar to that of the 
female; that the hard dark brown integument becomes thin and 
pliable and lightly pigmented; that the patterns formed by the 
minute spines on the terga and sterna assume the arrangements 
characteristic of the female; that the sternum of the eighth 
abdominal segment is almost divided into two plates, while that 
of the ninth often separates completely, forming two minute, 
lateral sclerites; that the tergum and pleura of the ninth seg- 
ment fuse, increase in length, and partially assume the form of 
the corresponding sclerites of the female. 
In the females the parasites do not cause the abdomen to 
increase in size or change its form in cross-section. However, 
the integument becomes thinner and there is some loss in pig- 
mentation. Since in the female the pigmentation is normally 
much less intense than in the male and the cuticula more pli- 
able, these changes are not nearly so radical as those in the male. 
The arrangement of the minute hairs on the abdominal sclerites 
remains unaltered in the female. The sternum of the seventh 
abdominal segment is not so deeply notched at its caudal border 
and that of the eighth segment only partially divided into two 
sclerites by the ovipositor, which is much shortened. The form 
of the tergum of the ninth segment remains unchanged, while 
the pleura decrease in length. 
D. The genital appendages 
As has been intimated in the foregoing pages, the external 
genitalia suffer a considerable reduction in size in parasitized 
individuals of both sexes. This is quite in contrast in the male 
to the reaction of the extragenital secondary sexual characteris- 
