INSECTA. 315 



order 1 . The most have no proper head, but a very moveable mouth 

 well adapted for extension, and two horny hooks curved downwards. 

 The skin of the larva when it changes to a pupa is not cast, but 

 becomes hard, and is changed into the covering of the pupa ; the 

 anterior extremity becomes thicker and rounder, and the whole 

 recalls the form of an oval keg. The perfect insect, by moving its 

 head, which is extended forward like a bladder, breaks this shell at 

 its upper extremity, whilst a piece of it springs open like a lid. 



Few genera of this family are in the perfect state carnivorous, 

 most of them living on flowers and plants. 



Phalanx I. Proboscis in some very short, in others none, in 

 place of proboscis and palps three tubercles ( (Estrus L.) 



Larva? parasitic, some living beneath the skin, others in the 

 frontal sinuses, or in the intestinal canal of mammalia. 



a) Proboscis small. 



Genera : Cephenemyia LATE., Cuterebra CLAKK, LATE., Trypo- 

 derma WIEDEMANN. 



b) Proboscis none. 



Genera : Hypoderma CLAEK, ((Estrus MEIG.), (Edemagena CLAEK, 

 Cephalemyia CLAEK, Colax WIEDEM., (Estrus CLAEK, (Gastrus 

 MEIG.) 



Note. Antennae triarticulate, with seta naked in most, in Cute- 

 rebra plumose. Gastrus MEIG. differs from (Estrus MEIG. by the 

 naked poisers, and wings without a transverse nervure at the apex. 



Comp. CLAKK, Observ. on the genus (Estrus, Trans, of the Linn. Soc. in. 

 1796, p. 289, &c. ; the same, An Essay on the Bots of Horses, &c., London, 

 1815, 4to, with fig. ; the same, On the Insects called Oistros by the Ancients, 

 Trans. Linn. Soc. xix. -2. 1843, PP- 81 94. 



A. NUMAN Waarnemingen omtrent de horzelmasTcers, welke in de maag 

 van het paard huisvesten, Amsterdam, 1834, 4to, mit pi. 



J. L. C. SCHBCEDEK VAN DEE KOLK, Memoire sur I'Anatomie et laPhysiol. 

 du Gastrus equi } Amsterdam, 1845, av. pi. 



Sp. (Estrus equi FABR., Gastrus equi MEIG., GUERIN, Iconogr., Ins. PI. 101, 

 fig. 5, CLAKK, Essay on the Bols, PI. i. figs. 13, 14, (LINN.EUS described 

 this species under the name of (Estrus Bovis). About 5 lines long, body 



1 In these BOUCHE has frequently observed a moulting ; Beitriige zur InseldenTcunde, 

 in Nov. Act. Acad. Gees. L. Car. Tom. xvn. i. 1835, p. 498. 



