PHTHIRUS INGUINALIS. 185 



Class XI.— INSECTA. (Insects.) 



Articulated animals with six legs, respiring by means 

 of tracheae ; head distinct from the thorax ; antennae 

 two. 



PHTHIRUS INGUINALIS. 



Crab-Louse. 

 Pl. XXV. fig. 3. 



Order Parasita. Family Siphunculata. Latr. 



Gen. Char. Anterior pair of feet simple, two hinder 

 pair didactyle ; thorax extremely short, scarcely 

 visible. 



Spec. Char. Body whitish. 



Pediculis pubis ; Lin. Syst. i. p. 1017. Lc Morpion ; Geoff. Hist, des Ins. ii.p.597. 



Pou <lu Pubis; Latr. Hist, des Crust, viii. p. 94; Redi, Exper.t. 19, f.l. 

 Le Morpion, Fr. ; Piattola, It.; LarW/a, Sp.; Piolho ladro, Vort.; Die Filzlaus, 

 la 1 1 laus, Ger.; Flatlus, Swed. ; Plotschiza, Russ. 



This disgusting parasite inhabits the eye-brows, pubes, &c. of men 

 and women, and is distinguished by the cheliform structure of its 

 legs, whence its name of Crab-louse. It is a frequent cause of 

 local prurigo ; for these animals perforate the cuticle, and stick so 

 close that they can with difficulty be dislodged. They are chiefly 

 discoverable by their nits, which may be seen attached to the basis 

 of the hairs, the insects themselves appearing only like discoloura- 

 tions of the skin. They are furnished, like the rest of the family 

 Pediculidse, with a mouth consisting of a tubulose very short 

 hanstcllum, but they have no mandibles, properly so called. The 

 body is fiattish, more round than the common louse, with a shorter 

 thorax, and the hinder pair of feet didactyle and very strong. 



