66 



ZOOLOGY 



intestine of the horse they get abundant food, and there 

 they develop. The larvae of another species, " the ox- 

 warble " or "grubs," are taken into the mouth of cattle, 

 and live for a time in the oesophagus. Then they bore 

 their way through the walls of this tube, and travel on 

 until they make their way out through the skin to the 

 surface. Another injurious species is the sheep bot-fly, 

 whose larvae cause " staggers " in sheep. 



The Syrphidae, 1 like the bot-flies, mimic honey-bees, 

 bumblebees, and wasps. 2 The adults feed on the pollen 

 and nectar of flowers, and even imitate the humming of 

 the bee. The larvae of some forms feed upon plant-lice ; 

 others, upon decaying vegetable matter. They may occupy 

 the nests of various stinging Hymenoptera. The larvae 

 of some species are known as rat-tailed maggots on account 



1 of their having a characteristic append- 



l^jjjf age. These are sometimes found floating 



jHBMp** iii foul water or even in salt water. 



The robber-flies (Asilidae 3 ) are usually 

 jlHwl f large size, have a short head, prominent 



eyes, legs covered with stiff hairs, and 

 abdomen either long and slender (Fig. 

 - 1 65), or stout. These flies attack and de- 

 vour other flies and even insects much 

 larger than themselves, such as bumble- 

 bees and dragon-flies. 

 The horse-flies (Tabanidse 4 ) include the large mourning 

 horse-fly, Tabanus astratus, which is of a uniform black 

 color, the white-lined Tabanus, T. lineola (Fig. 66), and 

 the smaller golden-headed horse and ox flies with banded 



1 cru/>06s or fftp<f>os, a small winged insect. 2 Fig. 64. 



8 From asilus, a gadfly. 4 From tabanus, the gadfly of Pliny. 



FIG. 65. Robber- 

 fly. Nat. size. 

 Photo, by W. H. 

 C. P. 



