156 MEDICAL ZOOLOGY. 



The larvae of the gall insect are apodal. Some live five and six months, 

 then descend to earth and assume the condition of nymph. Others go through 

 all their changes in the gall itself. 



Species. C. quercus tindoria, C. kollari, C. rosce, C. longipennis, C. 

 msana, C. polycera, C. hungarica. 



POLEX (Flea). Hemiptera. Mandibles and lingua long, setiform ; maxillae 

 small, triangular, palpi four-jointed ; labium minute, palpi three-jointed. 

 Body compressed. Antennae short with three joints, the last large, flat, 

 serrated, received in a small cavity, and covered with a scale. Max. palpi 

 with four joints, porrect. Post, feet saltatory. Tarsi with five joints. 



Four small round plates, situated between last two segments of thorax ; 

 post, pair largest, and represent rudiments of wings. Eyes two, simple ; 

 wanting in P. vespertilionis. No marked distinction between thorax and 

 abdomen. 



Development. $ twelve eggs, rounded, whitish color; larvae, grubs with 

 thirteen joints, last two hooked. Twelve days as inactive pupae. 



P. irritans (Common flea). 



P. penetrans (chigue, chigger, jigger). The 9 and do not attack man 

 prior to impregnation. After this, introduces itself under the nails or 

 between toes of feet ; causes a white globular vesicle, by rapid growth of 

 larvae, which are contained in a sac attached to abdomen by mother. In 

 treating this condition the small orifice is gradually dilated and the objects 

 removed. Scotch snuff or capsicum then placed in wound. 



PEDICULUS (Louse). Diptera. Antennae as long as thorax ; sucker is an 

 inarticulate sheath, armed with retractile hooks; eyes simple; abdomen 

 notched at borders. 



P. capitis. Thorax distinct, elongate, quadrangular, narrower than ab- 

 domen ; seven segments notched at margin ; stigmata upon six ant. segments, 

 circular, and furnished with a small opening in the middle. Stigma between 

 first and second pairs of feet is often indistinct, and resembles a papilla. 

 Color varies, livid or pale gray, and is said to adapt itself to that of the 

 hair ; all the segments are blackish on the margins. In the human louse, 

 transverse ridges; feet similar; tarsus one joint, bears a large claw on its 

 outside, and on its inside two straight, thick, horny stumps, and a large bris- 

 tle. (Esophagus short ; stomach longish ; two caecal appendages ; intestine 

 slightly sigmoid, receives four urinary vessels at its extremity, and passes 

 on into the pyriform large intestine. 



$ fewer; last abdominal segment is prominent and rounded off, furnished 

 on its dorsal surface with a valvular opening, beset with an abundance of as- 

 perities, anal and vaginal ; two pairs testes ; simple, wedge-shape penis, base 

 upwards, apex outwards, opens on back, chitinous. 



9 apex caudal not notched ; two lobes, between which is the anal aper- 

 ture ; two ovaries consist of five tubes each, forming two oviducts emptying 



