316 CLASS VIII. 
hairy, yellow, thorax in the middle black, wings with a brown-grey, trans- 
verse stripe in the middle and two similar spots at the point ; the female 
has a long black ovipositor at the end of the abdomen. This fly lays her 
yellow eggs in various situations on the hair of the horse, to which they 
remain firmly attached by a glutinous fluid. The young larve come from 
the eggs, which spring open by a lid, as very long and active little worms, 
and are conveyed by the lick of the horse’s tongue into his mouth and 
gullet (with respect to those eggs which lie beyond the reach of the tongue, 
we may suppose, with Numan, that the larva themselves creep to other 
situations nearer the head). Subsequently the larve live in the stomach of 
the horse, to which they have become attached in very great numbers 
(several hundreds at once). Here they remain several months, from spring 
till the beginning or middle of summer, then are detached, being expelled with 
the excrement, and change into pupe, from which, after about five weeks, 
the perfect insect comes to view. This species is found in the horse and 
ass ; besides these, and sometimes simultaneously with them, larvze also of 
other species (Gastrus hemorrhoidalis for instance) live in the same resort ; 
the larvee of this last species are smaller and deep red; see NumAy, Pl. 11. 
hor. 
(Estrus bovis Fasr., Mrtc., GuaRIN, Jconogr., Ins. Pl. 101, fig. 3, CLARK, 
1.1. Pl. i. figs. 8, 9, Cuv. R. An., éd. ill., Ins. Pl. 176, fig. 2. The larva 
of this species lives under the skin of the bullock ; that of @strus (Cephale- 
myia) ovis L., GuiRIN, Jcon. Ins. Pl. rot, fig. 4, MEIGEN, Syst. Beschr. Iv. 
Pl. 38, fig, 16, lives in the frontal sinuses of the sheep. 
Phalanx II. Proboscis distinct. ‘Two sete of haustellum. 
A, Muscarie (species from genus Musca L.) Proboscis distinct, 
membranous, retractile, bilabiate at the point. 
Though the Fly genus (J/usca), thus defined, be much smaller 
than that of Linnaus, it is still a very extensive group, in which 
the moderns distinguish many genera. Here may be compared 
Ropineau Desvorpy, “ssai sur les Myodaires, Mém. présentés a 
VAcad. des Sc. de Institut de France, Tom. 11. 1830, 4to. 
1 A species is spoken of in man: Wstrus hominis (Gmet., Syst. nat. Ed. 13, I. 
p. 2811); comp. Kirpy and Spence, Jntroduc. to Entomol. 1. pp. 136, 137. Of later 
observations Ist. GuoFFROY SatnT-HiLaIRe has given an account in the Ann. de 
la Soc. Entom. u. p. 518. That larve of Wstrus bovis and of other Diptera may 
sometimes live under the skin of man is probable from some observations ; a few years 
ago an insect was shewn me that had come out of a boil under the skin in a girl, 
it was the pupa of a dipterum, and agreed very well with that of Wstrus. A 
larva which in many respects resembled that of a Tachina, but yet differed from all 
the species of larvee of Diptera yet known, was observed by Dr Smirr; this larva 
was pressed from a boil on the head of a girl 63 years old; see J. J. Smirr and 
C.J. SunpEvatn, Vetersk. Akad. Handlingar, Stockholm, 1840, pp. 63-—68. 
