228 PARASITES. 



and another on the prothorax. On the flea of the hedgehog the 

 fringe is found on the mesothorax. 



Theobald, in his British Fiies, points out that the three seg- 

 ments of the thorax are very distinctly marked. On the second, 

 or mesothorax, is the first pair of scales or rudimentary wings, and 

 on the metathoracic segment we find the large scales representing 

 the halteres of the diptera. He goes on to say : — "This is a point 

 worth noticing, that the posterior rudiment is more developed than 

 the anterior, contrary to the usual arrangement in flies." 



In most of the fleas from various animals which 1 have exa- 

 mined, the mouth-parts appear to be almost identical, the piercing 

 instruments being about the length of three and a-half joints of 

 the maxillary palpi ; but in a female one from the badger they are 

 fully half as long again. 



The Pulicidce are divided into three genera, and number thir- 

 teen species in all. Their geographical distribution, like the -gnats, 

 reaches from the Arctic regions to the equator, but they seem to 

 flourish best in warm climates ; and, unlike the gnats, the male is 

 as eager for blood as the female. There is another flea (Fulex 

 penetrans), commonly called the Chigoe, or Sand flea, which is very 

 troublesome in South America, the West Indies, and on the West 

 Coast of Africa. They burrow into the flesh, and if not carefully 

 removed, in time lay their eggs under the skin, causing very serious 

 ulcerations. I have not been able to procure a perfect specimen, 

 but received the head of one from Trinidad, and mounted it. 



The true lice belong to the sub-class Ametabola, order Ano- 

 plura, the young not passing through a metamorphosis, and differ- 

 ing from the adult chiefly in size. They are destitute of wings, 

 have two simple eyes, and are parasitic on mammals. The rostrum 

 is retractile, concealed beneath the head, when at rest, consisting 

 of a soft tubular sheath, dilated at the end, armed with a double 

 row of small horny hooks, from the centre of which proceed four 

 bristles converging at their points, and forming a tube adapted for 

 suction. Their eggs are known as nits. 



In the ordinary head-louse the legs are all formed for climbing. 

 The claws at the extremity are exceedingly strong, and can oppose 

 each other so as to give a very firm hold on hairs, etc. They are 

 not at all well adapted for walking — a specimen was given to me 



