SIPHON APTERA 



859 



and the epimerite. The episternite has the anterior and ventral portion 

 separated off by an obUque incrassation to form a sternite. The prosternite, 

 or sternite of the prothorax, is not divided. Generally these various sclerites 

 show bristles. 



With regard to the abdomen, the first to seventh segments are more or less 

 normal, but the eighth to tenth are modified sexually. The tergites of the 

 second to the seventh segments are normal, carrying bristles and combs in 

 different species. The seventh tergite has a subapical bristle. The first 

 segment has no sternal sclerite, hence the first visible sternite belongs to the 

 second segment. The third to the sixth sternites carry a ventral row of 

 bristles. The seventh has a considerable number of bristles. The sexually 

 different segments must be considered according to sex. In the female the 

 eighth tergite is very broad ventrally, but the sternite is reduced to an 

 elongated plate lying between the ventral edges of the tergite. 



The ninth tergite carries the sensory plate, with usua'lly fourteen (there 

 may be more) setiferous grooves. The ninth sternite is membranaceous 

 laterally, and extends far ventrally, where it is strongly chitinized, and lies 



Fig. 451.— Anatomy of a Flea. 



(From the Journal of Hygiene, 1906.) 



I, Mouth; 2, pharynx; 3, salivary glands; 4, stomach; 5, Malpighian 

 tubes; 6, intestine; 7, rectum. 



inside the seventh or eighth segment. It forms the ventral wall of the vagina, 

 which is joined just anterior to it by the duct of the receptaculum seminis. 



The tenth tergite carries a short conical stylet, while the sternite, which is 

 triangular, carries a long bristle ventrally before the apex and shorter bristles 

 at the apex. 



The eighth tergite of the male is small, while its sternite is large, and from 

 its cavity the copulatory organs project. The accessory genital organs 

 belong to the ninth segment, the sides of whose tergite form the clasping 

 organ laterally. The internal ventral angle of the clasper is prolonged into 

 a manubrium, above which is a tubercle-like projection. The outer side of the 

 clasper has three processes, which are different in Pulex and Lcsmopsylla. 

 The ninth sternite has an internal vertical arm and a ventral horizontal arm. 

 The latter appears beyond the eighth sternite. The penis can be seen between 

 the ninth sternite and the claspers. 



Internal Anatomy. — The mouth, which is situate below the base of the 

 labrum, opens into the aspiratory pharynx, which communicates, via a long 

 oesophagus, with the stomach. Just before this organ the oesophagus is 

 swollen into a bulb, which represents the proventriculus. 



At the junction of the stomach with the intestine are the openings of the 



