580 MODERN CLASSIFICATION OF INSECTS. 
fall to the ground, in which they undergo their changes ; the front of 
the larva skin forming a kind of flat cap, on scaling off which the head 
of the real pupa is seen ( fig. 133. 1.). 
These variations in the larve of these three species render the es- 
tablishment of at least three genera requisite for the British species. 
In the very admirable memoir of Fischer ample details are given of 
the larve of the CE. Bovis and Ovis. 

The second general section of the order Diptera, or those forming 
the fifth stirps, is composed of a small group of parasitic insects of 
very peculiar structure, forming the Linnean genus Hippoposca* 
Fig, 133. 


( jig. 133. 2. Hipp. equina) ; and differing from the flies composing 
the former section, in the structure of the mouth, the immersion of the 
antenne within the head, and of the latter within the front of the 
thorax ; the denticulation of the tarsal claws, and the nature of their 
transformations. 
These differences, with others of minor importance, induced La- 
treille to form these insects into a primary section, which he at first 
named Coleostoma (fist. Nat., t. ii. 365.), and afterwards Eprobos- 
cidea. This name Dr. Leach, who considered these differences suf- 

* Brsutiocr. Rerer. To tHE Hiproposcipe£. 
Slabber, in Verhandel der Maatsch. te Haarlem. Deel 10. St. 2. bl. 413. St. Hi- 
rundinis. 
Leach, on the Gen. and Spee. of Eproboscideous Ins. in Wernerian Trans. vol. ii. 
Nitzsch. Die Fam. und Gatt. d. Thierinsekten, in Germar’s Mag. d. Ent. vol. iii, 
Modeer, in Gotheborgska Handlung. Vetenskap. St. 3. p. 26. 
Dufour. Rech. Anat. sur ?PHippoboseca equina, in Ann, Sci. Nat. tom. vi. — 
Ditto, Déser. n. s. Ornithomyia in ditto, tom. x. 
