248 NATURAL HISTORY 



extremely irksome and injurious to them. These are 

 the Hippobosca Hirundinis 3 t with narrow subulated 

 wings, abounding in every nest; and are hatched by 

 the warmth of the bird's own body during incubation, 

 and crawl about under its feathers 4 . 



A species of them is familiar to horsemen in the 

 south of England under the name of forest-fly ; and to 

 some of side-fly, from its running sideways like a crab. 

 It creeps under the tails, and about the groins, of horses, 

 which, at their first coming out of the north, are ren- 

 dered half frantic by the tickling sensation ; while our 

 own breed little regards them 5 . 



[Craterina Hirundinis, OLF.] 



4 The Hippobosca Hirundinis of the text is now referred by entomologists 

 to a genus established by Olfers for its reception ; it stands in the syste- 

 matic lists under the name of Craterina Hirundinis, OLF. The house- 

 swallow is principally and seriously infested by its annoyance: 



The swift, differing in genus from the swallows, appears to have its 

 peculiar genus of insects appropriated to it ; that which has been named 

 by the Rev. W. Kirby, Oxypterum: 



The forest-fly again, attached to a different race of animals, belongs 

 also to its own genus in the insect class ; and for this has been retained 

 the name of Hippobosca, originally applied to the whole of these pests : 



The sheep, and perhaps the deer, are obnoxious to the attacks of ano- 

 ther genus of the same family of insects ; the Melophagvs of Latreille : 



The black grouse, the crow, and other birds are infested by yet another 

 genus of the same group ; Ornithomyia, LATR. : 



And an allied genus, Nycteribia, LATR., is appropriated to the Bats. 



The genera enumerated, with the addition of that named by Mr. Cur- 

 tis H<etnobora, the precise habitat of which has not yet been ascertained, 

 constitute the class Omaloptera of Dr. Leach, so far as it has yet been 

 observed in this country. This class has been removed from among the 

 Diptera, chiefly on account of the nature of its metamorphosis : the larva 1 , 

 instead of being free, as in the Diptera, and seeking their own nourish- 

 ment, being in the Omaloptera nourished within the abdomen of the mo- 

 ther : when fully grown they are passed in the form of a pupa covered 

 with the indurated skin of the maggot. 



Besides the several species of swallows and the swift, it will thus be 

 seen that other birds are annoyed with insects which have been, until 

 recently, considered as Dipterous; such have been found on the crow, the 

 black grous, the tit-pippit, the yellow hammer, &c. &c. E. T. B. 



* In the New Forest in Hampshire, whence its name of forest fly, 

 the Hippobosca equina, LINN., abounds in such profusion that Mr. Sa- 

 luouelle states, in his Entomologist's Useful Compendium, that he has 



