APHANIFTERA. 29 



fleas are, however, generally classified at the present day as the first 

 sub-order of the Diptera, namely, the Diptera Aphaniptera, being thus 

 placed between the Hemiptera Anoplura, or lice, and the Diptera 

 Nemocera. Verrall, in his list of British Diptera (1888), places them 

 in the Nemocera. 



Pulex irritafis, L. (the Common Flea). 



This is the best-known of all the Pidicidce, and has been described 

 over and over again. The following entomologists have given the 

 best descriptions : Leach, Duges, Bouche, Rosel, De Geer, Latreille, 

 Newman, Kirby, and Westwood, and the works of these authors may 

 be consulted for more detailed accounts. 



The abdomen large, inflated, reddish-brown, with two apical 

 diverging bristles. Bristles developed on each segment, especially 

 on the dorsal surface and around the genitalia. Head short and 

 shining, minutely punctate. Antenn?e usually carried in the recep- 

 tacles ; basal part of maxilla thickened ; palpi composed of four 

 nearly equal joints. Mandible thickened and horny on one side, 

 with small denticles ; thin and hyaline on the other, with numerous 

 deep denticulations. 



Legs paler than the body. Coxje broad and flat, with a few 

 scattered bristles on the upper surface. Femora also broad and flat, 

 hairy ; a fringe of bristles on the inner side of the hind pair. Thick 

 apical spines on the tibiae and tarsi. Ungues fringed on the under 

 surface by little spines (?). The first tarsal joints in the hind legs 

 are the largest ; the fifth joints next in size ; the second, third, and 

 fourth in decreasing succession. The two fore legs are differently 

 constructed, two and five being the largest joints ; the first, third and 

 fourth being nearly equal. The last tarsal joint always armed on the 

 under surface by a few spines — generally four in the common flea. 



The Pygidium is composed of disc-like areolae, around which is a 

 ring of rectangular rays. 



The male is armed with two stylets for copulation. The mode of 

 copulation may easily be seen, by keeping a number of fleas in a glass 

 test-tube. The coupling takes place tail to tail, the female (which 

 is much larger than the male) stands over the male. The pairing 

 sometimes only lasts a few seconds, but usually much longer. 



Leewenhoeck first discovered the spermatozoa of the flea. He 

 described them as " serpent-like animalcules." The flea may easily 

 be dissected in water under the microscope, and the alimentary canal, 

 testis, ovary, etc., easily seen. 



They are best mounted in balsam, after being well soaked in 



