FLIES AND FLEAS. 609 



DIPTERA APHANIPTERA. 



This section includes the fleas, which are too well known to need descrip- 

 tion. The species are not well-defined, and it is *hot clear how far those 

 which are found on different animals are really distinct. 

 They are all remarkable for their great powers of leaping ; Fleas. 



and they possess the merest rudiments of wings. They 

 sometimes form colonies on the ground, especially in warm countries, and 

 have been observed to attack caterpillars, so that their food is not confined 

 to the blood of mammals or birds. They are probably quite as ready to 

 attack any soft-bodied animal which comes in their way. I have already 

 suggested (antea, p. 596) that it is possible that they may even attack the 

 common bed-bug, and exterminate it in houses where they are sufficiently 

 numerous. In America it is said that the common house-flea is the dog- 

 flea, the human flea being much less common. 



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