514 DIPTERA CHAP. 



dreaded migratory Locust Schistocerca peregrina in great quantities, 

 by the larvae eating the eggs of the Locust. The female of this 

 fly, in order to reach the desired food, penetrates from one to 

 three inches below the surface of the ground. 



Fam. 39. Oestridae (Bot-flies). Rather large or very large 

 flies, with extremely short antennae, bearing a segmented arista, the 

 front of the head prominent, the posterior part of the wings fre- 

 quently rough, and with but few veins : the mouth usually atrophied, 

 the trophi being represented only by tubercles ; larvae living in Verte- 

 brates, usually Mammals, though it is possible that a few occur in 

 Birds and even in Reptiles. This is a family of small extent, less 

 than 100 species being known from all the world, yet it is of 

 much interest on account of the habits of its members, which, 

 though of large size, live entirely at the expense of living Verte- 

 brates, to the viscera or other structures of which they have definite 

 relations, varying according to the species. Some (Gastrophilus,eie.} 

 live in the alimentary canal; others (Hypoderma, etc.) are encysted 

 in or under the skin; while others (Oestrus, etc.) occupy the respir- 

 atory passages. As many of them attack the animals used by man, 

 and some of them do not spare man himself, they have attracted 

 much attention, and there is an extensive literature connected 

 with them ; nevertheless the life-histories are still very incom- 

 pletely known. Indeed, the group is from all points of view a 

 most difficult one, it being almost impossible to define the family 

 owing to the great differences that exist in important points. 

 Some think the family will ultimately be dismembered ; and 

 Girschner has recently proposed to treat it as a division of 

 Tachinidae. The chief authority is Brauer, in whose writings 

 the student will find nearly all that is known about Oestridae. 1 

 Some of them exist in considerable numbers (it is believed that 

 they are now not so common as formerly), and yet the flies are 

 but rarely met with, their habits being in many respects peculiar. 

 Some of them, for purposes of repose, frequent the summits of 

 mountains, or towers, or lofty trees. Some have great powers of 

 humming ; none of them are known to bite their victims, indeed 

 the atrophied mouth of most of the Oestridae forbids such a pro- 

 ceeding. Some deposit their eg^s on the hairs of the beasts from 



1 We niay specially mention the monograph of Oestridae, published in 1863 by 

 the K. k. Zool. - Hot. Ges. Wlcn, and supplements in Wien. cut. Zeit. v. vi. 1886, 

 1887 ; these include copious bibliographic lists. 



