3 2 4 THE STUDY OF INSECTS 



the larvae become full-grown in from five to seven days, having 

 molted twice; the pupa state lasts from five to seven days. There may 

 be in the warm season a generation each month. Since the fly picks up 

 the germs of typhoid fever in the filthy places where it breeds and carries 

 them to our kitchens and dining rooms, it is a dangerous fly and should 

 be destroyed wherever possible. The fifth longitudinal vein (Mi +2 ) turns 

 abruptly upward at the end (Fig. 566). 



The stable-fly, Stombxys calcitrans. — This species resembles the 

 housefly in appearance, but it is a trifle larger and has its mouth-parts 

 fitted for piercing and for sucking blood. It annoys cattle greatly; and 

 before storms and in the autumn it enters our dwellings and attacks us. 

 The popular belief that the housefly bites more viciously just before a 

 rain is due to invasions of this species at such times. The mouth-parts 

 of the true housefly are not fitted for piercing. 



The horn-fly, Hcematobia irriians. — This is an exceedingly annoying 

 pest of horned cattle. It resembles the housefly in appearance, but is 

 less than half as large. These flies cluster in great numbers around the 

 base of the horns; they also settle upon the back. The larvae live in 

 fresh cow-manure. 



The tsetse-fly, Glosslna morsitans. - — This species, which is closely 

 allied to the stable-fly, is widely distributed in Africa and is the carrier of 

 the blood parasite that causes the disease of cattle known as " nagana." 

 The closely related species, Glosslna palpalis, carries the blood parasite 

 which causes the sleeping sickness of man. 



THE PUPIPARA 



There are several families of related flies in some of which, at least, 

 the larva? attain their full growth within the body of the female fly and 

 within a few hours after the larvae are born they change to pupa?. It was 

 formerly supposed that the young were born as pupae hence the name, 

 Pupipara. 



The adult flies are parasitic and live like lice on the bodies of birds 

 and mammals. Two species are parasites of the honey-bee. The wings 

 are well developed in some forms while in others they are vestigial or 

 wanting. 



Family Hippoboscid^; 



The Louse-flies 



The louse-flies are very abnormal flies that, in the adult state, live 

 like lice, parasitically, upon the bodies of birds and mammals. Some 

 species are winged, others are wingless, and still others are winged for a 

 time and then lose their wings. 



The sheep-tick, Meldphagus ovinus. — This well-known 

 pest of sheep is the most common member of the Hippo- 

 boscidae found in this country. It is wingless and its halteres 

 are vestigial (Fig. 567). It is about \ of an inch in length, 

 of a reddish or gray-brown color, and with the entire body 

 fig. 567. covered with long bristly hairs. This pest is often very in- 

 jurious, especially to lambs after shearing time, as it tends to migrate 

 from the old sheep to the lambs at this period. 



