48 FLEAS. 



difference of shape was very observable in the specimens sent me last 

 autumn. See p. 44. 



Of the habits of the House Flea (P. irritans), quoting from various 

 observers, it appears that the larvae, or maggots, attain full growth in 

 about eleven or twelve days, and occupy about twelve more days in 

 maturing in pupal state, from which the perfect Flea develops, at first 

 as whitish in colour, but soon assumes its brown colour. In winter, 

 the time of development, even in a warmed room, is somewhat longer. 



The Cat and Dog Flea (P. serraticeps, Gerv.) may be distinguished 

 from the House Flea [P. irritans) by the presence of "combs of spines 



Pdlkx sekraticeps, magnified, and line showing natural size. 



on the border of the head and pronotum " * ; a comparison of the edge 

 of the head and of the segments bebind the head in the figures of 

 Fleas given at p. 44 and above will show this difference clearly. This 

 kind is said to be generally distributed, "practically over the entire 

 world"; but as in general appearance (to mere examination by the 

 naked eye), and also in habits, it much resembles the House Flea, it 

 seems unnecessary here to go into miuutife. 



There are various other kinds, as Pulex avium, Tasch., infesting 

 many birds, including domestic poultry ; P. fasciatus, Bosc. d'Autic, 

 or Eat and Mouse Flea ; P. sciurorutn, Bouche, infesting squirrels (in 

 Europe); P. (loniocephalus, Tasch., and other species, which are not 

 now (though they formerly for the most part were) included in the 

 single family of PtiUcidce, which has now been more specially restricted 

 to the forms " in which the female abdomen does not become swollen, 

 and the labial palpi are from three- to five- jointed." f 



In the above notes I have tried, to the best of my power, to give 

 some main points of information brought up to date, and which may, 

 I trust, be found reliable. But those who search the accounts 

 generally referred to will appreciate the great difficulty of reconciling 

 many of the statements, not only as to position of the family and its 



* Pronotum, the upper part of the prothorax — that is, the foremost division of 

 the fore body. 



t See ' Insects Affecting Domestic Animals,' previously referred to, p. 142. 



