PEDICULINA. 553 



In Aradus the beak is longer than the head, the prothorax 

 is widely expanded, while the wing-covers are rounded at the 

 base. A. crenatus of Say has the cylindrical edge of the abdo- 

 men obtusely crenated. The species are found under the bark 

 of trees. 



Pediculina Burmeister. Lice. In these low degraded Hem- 

 iptera, which stand in the same relation to the rest of the 

 Ileniiptera as the Flea does to the more perfectly organized 

 Diptera, the body is wingless, with a small indistinctly jointed 

 thorax, while the abdomen is large, oval, with nine segments. 

 The antennae are filiform, five-jointed, and the eyes are minute, 

 not faeeted. The tarsi are two-jointed, with a large hook-like 

 terminal joint, which is bent back towards the basal joint. 

 The mouth-parts still preserve the form of a beak-like sucker, 

 but it is fieshy and retractile, and the body is white, and of 

 minute size. The species of Pedicidus are blood-suckers, and 

 parasitic on man and various species of Mammalia ; different 

 species being found on different regions of the 

 body. Different varieties, according to Dr. W. I. 

 Burnett, are found living on the bodies of diflferent 

 races of men. 



Two species live on man ; Pedicidus huma%us 

 capitis DeGeer (Fig. 558) inhabits the head, while 

 the Body Louse, P. corporis of DeGeer (P. vesti- 

 menti Nitzsch) is found elsewhere. These two 

 species are difficult to distinguish, they are so 

 closely allied. Professor J. C. Schiodte, a Scandinavian 

 naturalist, has recently published an elaborate treatise on this 

 genus, and describes the mode of attack used by these disgust- 

 ing creatures. It thrusts its wiinute beak into the skin, and 

 sucks in the blood by means of its large sucking stomach or 

 "pumping ventricle." Schiodte placed one of these insects 

 on his hand, and observed its movements through a glass. 

 After the creature had fixed its beak or haustellum into his 

 hand this naturalist noticed that "at the top of the head, under 

 the transparent skin, between and a little in advance of the 

 eyes, a triangular blood-red point appears, which is in contin- 

 ual movement, expansion and contraction alternatino- with 



