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after he had withdrawn, that a small portion of the tail end of the 

 animal was left untouched — no doubt in consequence of his being 

 unable to penetrate to the small end of the whorl of the shell — and 

 also the skin of the remaining part and the horny tongue-membrane. 



Several species of Tabanus are so prodigiously abundant in Illinois, 

 in districts remote from any large streams or ponds, that they must 

 evidently breed in the earth, like DeGeer's species, not in the water, 

 like mine. There are prairies in Central Illinois, as I am credibly 

 informed by numerous witnesses, across which it is impossible to ride 

 or drive a horse in the heat of a summer's day on account of the 

 Tabanus. The most troublesome species is rather larger than T. 

 lineola Fabr., and when alive, its eyes are of a brilliant emerald-green, 

 whence it is popularly known as the " greenhead." This species is 

 pretty common every year in the adjoining county of Henry, yet I 

 have never met with it in Rock Island County, 111., which lies imme- 

 diately north-west of Henry, though we have eight other species of 

 Tabanus, all rare but lineola ; and I believe it does not generally 

 occur in Northern Hhnois. Baron Osten Sacken has commented to 

 me on the singular fact, that, although Tabanidse are so numerous in 

 individuals, we scarcely ever meet with their larvse. But this wiU 

 not appear so remarkable when we reflect, that of the only two species 

 known in the larva state, one hides itself in the earth and the other 

 in the water. 



If, therefore, as appears from the above considerations, the larvae of 

 many, perhaps most, of our Tabanidse live in the ground, and if, as 

 there is every reason to suppose, the larvas of the terrestrial species 

 are as carnivorous as I have shown those of the aquatic species to be, 

 there can be little doubt, considering how numerous in individuals 

 many of the species are, that they must destroy, during their larva 

 life, innumerable noxious subterranean larvse, Melolonthadce, Lyttadoe, 

 Tipuladce, etc. They certainly cannot, at least in Illinois, feed habit- 

 ually upon land-snails, for land-snails are quite scarce in that State. 

 The scheme of the Creation is perfect, and Nature is never at fault. 

 It is only when Nature's system is but half understood that we heed- 

 lessly complain of its imperfections. We blame the house-flies for 

 annoying us, and fail to see that in the larva state they have cleared 

 away impurities around our dwellings, which might otherwise have 

 bred cholera and typhus fever. We execrate the blood-thirsty mos- 

 quito, and forget that in the larva state she has purified the water, 

 which would otherwise, by its malarial effluvia, have generated agues 

 and fevers. In all probabiHty, when we rail at the Tabani, that tor- 

 ment our horses in the summer, we are railing at insects which, in the 

 larva state, have added millions of dollars to the national wealth, by 



