ANOPLURA : THE LEGS 539 



provide a mode of exit from the body for a parasite. They are extremely 

 small, and cannot be recognized in dissections. 



Certain points regarding the nomenclature of the parts should be 

 noted, as the size and shape of the proboscis and sucking apparatus 

 are used as taxonomic characters. The part described in the fore- 

 going as the buccal cavity is termed by Enderlein the pharynx ; 

 its lateral thickenings are the fulturae. The length of the proboscis 

 (Riissel) is also taken into account. The chamber described as the 

 pharynx, and corresponding to the pharynx of the mosquito, is termed 

 by the same author the larynx. In the subsequent key and the 

 descriptions of the genera Enderlein's terms will be retained as in the 

 original. 



The sucking apparatus and the proboscis can be readily seen through 

 the integument in cleared preparations. 



The thorax is relatively small, and does not show complete segmenta- 

 tion. It is flattened dorso-ventrally, and is much more chitinized at the 



sides than on the dorsal or ventral surfaces. Usually 



f , . . . . , , The thorax 



there are strong bars or chitm passing inwards from 



the insertions of the legs to act as apodemes for the attachment of 

 muscles. In the middle of the ventral surface there is a single sternal 

 plate, the shape of which forms a useful distinguishing feature (Plate 

 LXVIII, figs. 5, 6 and 7). In nearly all the genera there is a single pair 

 of stigmata on the lateral borders of the mesothorax ; in some forms the 

 metathorax also bears stigmata, and rarely there may be a small one on. 

 the prothorax. 



The legs are strongly developed, in accordance with the mode of life 

 of the louse, which demands appendages adapted for clinging firmly to 



the hairs and skin of the host. How well they serve 



The legs 

 their purpose is demonstrated when one attempts to 



remove a louse from a rough piece of cloth. Each leg consists of a coxa, 

 trochanter, femur, tibia and tarsal joint. The coxa, which articulates 

 with the thorax internal to the lateral border, is broad and oval in 

 shape ; the trochanter is smaller and narrower ; the femur has the shape 

 of a short cylinder ; the tibia is large and stout, and is provided with a 

 thumb-shaped process at the inner side of its distal end, which opposes 

 the terminal claw in much the same way as that in which the thumb of 

 one's hand opposes the index finger. The tarsal joint is about the same 

 length as the tibia, or a little shorter, but is much thinner. It terminates 

 in a strong recurved claw, the concave side of which is roughened and 

 thrown into ridges. In Haematopinus there is a small triangular plate 



