ORDER DIPTERA. 125 



Family Hippoboscidae. The sheep-tick and horse- tick are known by 

 the flattened head and body, and by the stout proboscis. The 



FIG. 144. Bat-tick. Fio. 145. Sheep-tick and pnparium. 



sheep-tick, Melophagus omnus Linn., is often very troublesome to 

 sheep. The horse-tick (Hippobosca equina Linn.) is winged, with 

 large claws. 



Sub-order 2. Cyclorhapha. This name has been given 

 to this subdivision of flies from the fact that the perfect 

 flies escape from the pupa-case through a circular orifice. 

 The word " maggot" is especially applicable to the larvae 

 of this group, since they are worm-like, whitish, without a 

 definite head, and are footless. When about to pupate 

 their bodies shrink into a barrel-shaped form, and the skin, 

 instead of being cast off, forms a dense case for the protec- 

 tion of the soft-bodied, white pupa within. 



The types of the sub-order are such insects as the house- 

 and flesh-flies, as well as the Syrphus flies. The body is 

 short and thick, the abdomen conical and composed of 

 from five to eight segments. 



The arrangement of the families here adopted is that 

 of Osten Sacken's " Catalogue of North American Diptera" 

 (second edition, 1878), while the characters of the families 

 are taken from Loew's " Monographs of the Diptera of 

 North America," Part L, though the order of succession 

 has been reversed, the enumeration beginning with the 

 lowest and ending with the highest family. Certain of 

 the smaller, unimportant families are mentioned only by 

 name. 



