OUTLINES OF ENTOMOLOGY. 97 



Still another plague of the herds has recently appeared in this 

 country as an immigrant from Europe. This is the Horn-fly (Hcemato- 

 Ma serrata, Rob. — Des). From the accounts of Dr. Riley of Washing- 

 ton, and other eastern entomologists, we learn that it is a dark species, 

 much smaller than the house-fly, but otherwise much like it, which has 

 the habit of settling in swarms on the necks, shoulders, and around 

 the bases of the horns of cattle. It punctures the skin with its horny 

 beak and draws the blood, so worrying the poor animals that they be- 

 come reduced in flesh, and cows fail to give the usual quantity of milk. 

 The flies lay their eggs on the fresh droppings of the cattle, in which 

 the larvje breed. 



The large hairy "Blue-bottle" ^y f3Iusca cresar, Linn. J, and the 

 smaller Green "Meat-fly" fCalipJiora erythr(roephala, Meig.), are well. 

 known species which give much trouble to meat dealers and house- 

 keepers. 



The Screw-worm fly (Lucilia macellaria, Fabr.) has occasionally 

 proved fatal to human life by laying its eggs in wounds or in tl^e nostrils 

 of persons who were sleeping in the open air. It occursjn the South- 

 western States, where it is a great plague on cattle. 



The family Trypetidje includes a number of very pretty flies, 

 which have the wings variegated with smoky-brown spots and bands. 

 Many of these flies are gall-makers on various weeds, and are not 

 especially injurious. One, however (Trypeta pomonella, Walsh.), is the 

 parent of the Apple maggot, which has, in some of the Eastern States, 

 proved very destructive to apples, rivaling, and in some instances ex- 

 ceeding, the damage done by the Codling moth. 



The Onion fly (Tritoxa Jlexa, Wied.) is sometimes quite injurious to 

 growing onions. It has dark, oblong wings, crossed by three curving 

 white bands. It is now placed in the family Ortalid^. 



In the PioPHiLiD^ we find the Cheese fly fPiophila casei, Linn). 

 The family Dro^hilid^ includes several small species that attack 

 ripe and preserved fruits. In Oscinid^ are a few species injurious to 

 growing grain. Meromyza amencana^ Fitch., burrows in the tender 

 stalks. 



A third Sub-Order (Pupipara) has been grouped with the 

 more lowly organized Diptera, although the usually minute insects 

 composing it are not much like the typical flies. These are the Sheep- 

 tick ( Melophagus ovinus, Linn.) and the Horse tick ( Hippohosca equina 

 Linn.), which is the only winged species. Others, very minute, are the 

 Bat-ticks and Bee-lice. 



The Fleas also have many affinities with flies, and may here be con- 

 sidered in connection with them ; yet most authors now class them in a 



