The Hog Louse 645 



Several attempts have been made to feed the hee on guinea pigs, but 

 without success. The dense hair of the pigs hampers the movements 

 of the hce, and, if shaving be resorted to, the hce are left without a foot- 

 hold. If the finger be pricked and lice brought in contact with the freshly 

 escaped blood, the lice immediately move away. AVidmann (1915 b: 

 1337) described a similar reaction in man-infesting lice, which refused to 

 feed on various organs just removed from freshly killed mice. 



When placed on the arm, hog lice may feed at once or maj' move about 

 more or less rapidlv. When walking they appear to move sideways as 

 often as straight forward with the head in front. The peculiar structure 

 of the feet, first described by Osborn (1891:20 and 1901:1071, enables 

 the lice to grasp the hairs on the arm. The tibia (Plate LVIII, 1) increases 

 at the tlistal end to twice the width of the proximal end, and the dorsal 

 half only articulates with the tarsus. The remaining part is concave and 

 its ventral border is drawn out to a spur, bearing a stout spine at the apex. 

 In the concavity rests a stalked, protrusil-")le, subcircular pad bearing two 

 spines and two hairs. On the inner edge of the tar.sus, in hne with the 

 surface of the extended pad, is a blunt process bearing a spine. The 

 inner surface of the claw is slightly serrated. In holding a bristle or a 

 hair, the claw is bent over to rest on the tibial spur and the pad is pushed 

 against the opposite side of the bristle, thus preventing the insect from 

 slipping. Enderlein (1904:141), to whom Osborn's earlier descriiition 

 was evidently unknown, describes the pad as a strongly chitinized skeletal 

 piece of triangular shape. In specimens cleared in potash and mounted 

 under a cover glass it frequentlj- has this shape, while in living and in 

 uncleared specimens it always appears sulicircular. Enderlein names 

 this pad the pretarsal sdcritc, which name is retained by Neumann (1911: 

 407) in his description of the insect. 



The earliest description of a louse feeding is that of Hooke (1665:211- 

 213). He described the passage of lilood from his arm into a louse which 

 he had placed there after it had fasted for several ila^-s, and the working 

 of a pmuplike apparatus in the head. Swammerdani (1682, English 

 trans. 1758:33-35) gave a more detailed description, but he disagreed with 

 Hooke's description of the mouth parts, saying: " The louse has neither 

 beak, teeth, nor anj' kind of mouth, as Dr. Hooke descril^ed it, for the 

 entrance into the gullet is absolutely closed; in the place of all these, it 

 has a proboscis or trunk, or, as it maj- be otherwise called, a pointed and 



