APHANIPTERA. 353 



and structure, according to the species and even the sex of the 

 flea, I have prepared photographs of the antennae of J and $ of 

 Pulex avium, one of F. goiiiocephahcs, and one of P. erinacei, all 

 magnified to the same extent — viz., 200 diameters. 



Many species of flea have a number of spines on the back of 

 the prothorax, forming a sort of comb, and some have similar 

 spines on the sides of the face. These combs have the teeth 

 always directed backwards, and must greatly assist the fleas in 

 maintaining their hold among the hairs of the animals they infest, 

 and the probability that this is their use is strengthened by the 

 fact that the human flea alone is entirely devoid of them. 



At the extreme end of the flea's body is the pygidium, a circu- 

 lar plate with a division down the middle, in which are situated a 

 number of areolae, each containing several wedge-shaped eleva- 

 tions placed in a circle, and with a rather long hair or bristle 

 implanted in the centre. The spaces between these areolae appear 

 to be covered with small spines on the top of small tubercles. 

 These show rather indistinctly in F.goniocephahis, which is magnified 

 750 diameters, taken with ^-in. oil-immersion without ocular. 

 The addition of a projection ocular, which has increased the 

 magnification to 1,500 diameters, has, however, failed to disclose 

 any further detail. The pygidium of a flea is an excellent test to 

 judge of the defining power of an objective. 



The second genus, Hysirichopsylla, contains only one British 

 species — the Pulex talpce. of Bouche, Ceraiophyllus talpce of Curtis, 

 regarding which, however, Dale says, writing in the Eiitomologisf s 

 Monthly Magazine, in June, 1890, "It is quite certain that Talpce 

 is a misnomer, as it is not found on the mole." As I have not 

 been successful in obtaining a specimen, I pass on to the third 

 genus, Typhlopsylla, which contains four or five species, some of 

 them infesting bats. One species, T. assiinilis, is very common 

 on the mole. 



Not having as yet bred any fleas, I have no personal know- 

 ledge of their metamorphoses. It is said that each female lays 

 about a dozen eggs at a time. These are deposited in various 

 places, such as the cracks in boards, in carpets and rugs, on 

 the hairs of dogs and other animals, and in various other 

 places according to the species. These eggs soon hatch, and 



