THE FLY AND ITS ALLIES 71 



mosquito. Their legs are easily broken, and seem to be so 

 much in the way that flight is clumsy. The adults are 

 quite harmless, but some of the larvse are destructive in 

 that they feed upon tender plants and cause them to wither 

 and die. 



There remain to be considered a number of degenerate 

 flies degenerate because parasitic in the adult state. The 

 first family we may consider is that of the louse-flies, 1 or 

 Hippoboscidae. 2 These small insects have a firm proboscis 

 used for piercing, and stout legs. Only certain of the 

 genera develop wings, and some of these lose them after 

 they gain their hosts. They live, like lice, in the fur of 

 mammals or the feathers of birds. They are viviparous, 

 the larvae being ready to pupate at the time of birth. The 

 sheep-tick, Melophayuz* ovinusf is one of the best-known 

 forms. Diptera allied to the foregoing live as parasites 

 on the body of the honey-bee. 



Fleas (Aphaniptera 5 ) are likewise wingless, blood-suck- 

 ing parasites. The body is laterally compressed so that it 

 can move easily among the hairs of its host. The hind- 

 ermost' legs are strongest, and are used in springing. In 

 Europe the human flea, Pulex Q irritans? is a common pest, 

 but in this country the dog or cat flea is the one which 

 causes most inconvenience to man. The dog flea differs 

 from Pulex irritans in having a row of tooth-like spines on 

 the lower margin of the head. The fleas develop in dust 

 in the cracks of the floor and about the sleeping-places of 

 domestic pets. They may be combated by means of clean- 

 liness and Persian insect powder. 



1 Suborder Pupipara. 4 Relating to sheep (ovis). 



2 IWos, horse ; /360-Kw, to feed. 6 d0cu^s, invisible ; Trrepdv, wing. 



3 /jLrjXov, sheep (wool) ; (j>dyw, to eat. 6 Flea. 7 Irritating. 



