346 APHANIPTERA. 



possess the least rudifuent of a wi?tg, and this I hope to explain 

 presently. 



Westwood considered that the fleas formed a distinct order, 

 and he placed them between the Hemiptera and the Diptera, 

 being allied to the former in the structure of the mouth organs, 

 and to the latter in the metamorphoses they undergo ; and it is 

 now, I believe, generally considered that their true place is among 

 the two-winged flies. In the latest list of British Diptera, published 

 by Verrall in 1888, the order Aphaniptera is done away with, and 

 becomes a Family of Diptera, the PulicidcB. 



Fleas have long been the subject of very various researches ; 

 they have been considered from philological, from historical, and 

 from satirical points of view ; they have been celebrated for their 

 strength and for their jumping powers, and still more frequently 

 cursed for their bloodthirsty proclivities. They have been educa- 

 ted, and proved of considerable pecuniary profit to their instructors. 

 But of their real structure, of their life-histories, and their correct 

 classification, a great deal more knowledge remains to be worked 

 out. For a long time it was thought that the fleas of difl"erent 

 animals belonged only to a single species,* and, consequently, that 

 the human flea was not different from that of a cat or a dog. 

 So accurate an observer as Gilbert White writes in his History of 

 Selborne (p. 200), '* The sand-martin is strangely annoyed with 

 fleas ; we have seen fleas, bed-fleas {Pulex ii-ritans)^ swarming at 

 the mouths of their holes, Hke bees on the stools of their hives." 

 I need scarcely tell you that the flea found on the sand-martin is 

 as distinct from Pulex irritans as a thrush is from a blackbird. 

 Daniel Scholten,t of Amsterdam, showed in 181 5, by his micro- 

 scopical observations, that fleas differ from each other; and in 

 1832, Duges, of Montpelier, investigated the distinctive marks of 

 the various species. 



Regarding the number of species, however, we are stifl left in 

 the greatest uncertainty. WalkerJ describes fourteen, adopting the 

 names of the animals upon which, as a rule, they are found ; as 

 Pulex cants, P. felts, P. galli?ice, P. talpcE, and so forth. Verrall 

 in his list, though adding several new species not mentioned by 



* t Van Beneden, Animal Parasites, p. 127. 

 X British Diptera, Vol. iii., p. i. 



