192 ENTOMOLOGY FOR MEDICAL OFFICERS 



known as the pygidiunt ; in the female the sternum of this 

 segment forms the wall of the vagina ; in the male the sides 

 of the tergum form the large claspers, and the sternum forms 

 a complicated mechanism for the support of the large and 

 complex penis : all these sexually modified parts of the 

 9th segment, except the pygidium, are internal, though the 

 tips of the claspers project externally. The small tergum 

 and sternum of the loth segment form in both sexes the 

 roof and floor of the anus. The form of the claspers and 

 penis of the male show characteristic differences in the 

 different species, as do the number and disposition of the 

 bristles on the sides of the 8th tergum of the female. A 

 large bristle, or bristles, on either side of the /th tergum 

 project over and beyond the pygidium, and are known as 

 antepygidial bristles. 



L saliv.ql ifotnach malpijhian Tuhuk 



Zrecliim 



spcrmafb 



Fio. 74. — Alimentary Canal, etc., of Flea. 



Alimentary Canal (Fig. 74). — In the head there is an 

 elastic pharynx which works like a suction-pump, its cavity 

 when expanded by the contraction of certain muscles, forming 

 a vacuum. The gullet runs through the thorax, and expands 

 in the abdomen into a large and very distensible stomach, 

 the anterior end of which is muscular and valvular and is 

 known as the " gizzard." A short curved intestine runs from 

 the stomach to an enlarged rectum. At the junction of 

 stomach and intestine there are four excretory Malpighian 

 tubules. The salivary glands are two pairs ; their common 

 duct expands below the floor of the mouth to form a sort of 

 contractile reservoir from which saliva is ejected down the 

 salivary grooves of the mandibles when the flea " bites." 



Reproduction and Metamorphosis. — The female flea is 

 larger than the male and has a longer and more oval 



