OR FLEAS. 383 



including the head, which is of a horny texture, 

 living sometimes upon the bodies of animals, amongst 

 the hairs and feathers of which he twists about, or in 

 dusty places about the floors ; but in either case his 

 food consists of animal matter. When full-grown, 

 the larva encloses itself in a small cocoon of silk, in 

 the interior of which it undergoes its change to the 

 pupa state, on assuming which it casts its larva-skin 

 and has its limbs enclosed in separate cases. It remains 

 in the pupa state for about a fortnight, and then 

 emerges to commence its attacks upon our persons. 



Several species have been described, most of which 

 confine their attentions to particular species of mam- 

 mals and birds. According to various authors, the 

 Fleas which infest the cat and dog are distinct species 

 from that which favours us with its notice; but if 

 the three species be really distinct, I suspect they 

 are not very particular as to which animal of those 

 above mentioned they derive their nourishment from. 

 The mouse and rat have a pale -coloured species 

 (Pulex Musculi] peculiar to themselves, as have also 

 the common fowl and the pigeon (P. Gallinte and P. 

 Columbae) amongst our domestic animals*. 



* The most remarkable species of this group is the Chigoe or 

 Jigger (Pulex \_Sarcopsylld] penetrans) of South America and 

 the West Indies, the female of which buries herself in the skin 

 of the feet of men and dogs, generally under the nails. When 

 established in this position, her presence is at first by no means 

 disagreeable ; in fact, some people have described the sensations 

 produced as rather pleasant than otherwise; but in a little time 

 her abdomen swells to the size of a small pea, from the develop- 

 ment in its interior of an immense number of eggs, and the pain 

 and irritation thus caused soon become very great. The only 

 remedy is the careful extraction of the creature, as otherwise the 

 eggs are said to hatch in the wound, causing fearful ulceration 

 and sometimes death. 



