188 



PRACTICAL PARASITOLOGY 



while the two arms extend along the lateral surfaces. The free, 

 rounded ends of the arms of the dorsal and ventral splints overlap at 

 about the centre of each lateral surface, while the anterior edge of 

 each splint is overlapped by the posterior edge of the splint in front 

 of it. This arrangement permits of considerable distension of the 

 abdomen, such as takes place in all females, and especially in those 

 of Sarcopsylla, as a result of the development of the ovaries. 



The other abdominal segments, together with their splints, show 

 quite different conditions. There is no ventral splint upon the 1st 

 segment, the ventral splint of the 2nd segment forming the attach- 



FIG. 98. Pulex irritans. Female. 27 : 1. K, Head, with eye, antenna, and groove 

 of the antenna. I, II, and III, Thoracic segments. 1-9, Abdominal segments (9, pygidium). 

 At the front part of the head, upon its ventral surface, are the mouth-parts : m, maxilla ; 

 md, mandible ; mxt, maxillary palp ; ol, upper lip ; u, lower lip. Behind the mouth-parts 

 is the pleuron of the 1st thoracic segment with the 1st leg : c, coxa ; f , femur ; t, tibia ; 

 ta, tarsus ; tr, trochanter. The legs of the left side only are shown. (After a drawing 

 by A. Dampf.) 



ment of the thorax, while the dorsal splint of the first segment is 

 modified into a small triangular or square scale, which meets the 3rd 

 thoracic ring. The splints of the 8th and 9th segments vary according 

 to sex and species. In the male, the dorsal splint of the 8th segment 

 is broad ; it is very much prolonged towards the ventral surface, and 

 extends so far back as almost completely to cover the 9th segment. 

 The ventral splint is proportionately reduced in size, and in the female 

 it is very small indeed. 



In both sexes all that is visible of the 9th segment is a small 

 portion of the dorsal splint and the sense-organ or pygidium. The 

 pygidium is an area enclosed in a thick chitinous ring ; its surface is 



