INDIRECT BENEFITS DERIVED FROM INSECTS. 217 



with those of the order Diptera, whose larvae alone find their 

 nutriment in it ; the imago, which would be suffocated did it 

 attempt to burrow into a material so soft, only laying its eggs 

 in the mass. These also are more select in their choice than 

 the Coleoptera — not indeed as to delicacy, — but they do not 

 indiscriminately oviposit in all kinds, some preferring horse- 

 dung, others swine's-dung, others cow-dung, which seems the 

 most favourite pabulum of all the dung-loving insects, and 

 others that of birds. ^ The most disgusting of all is the rat- 

 tailed larva that inhabits our privies, which changes to a fly 

 (^Eristalis tenax), somewhat resembling a bee. 



Still more would our olfactory nerves be offended, and our 

 health liable to fatal injuries, if the wisdom and goodness of 

 Providence had not provided for the removal of another 

 nuisance from our globe — the dead carcasses of animals. 

 When these begin to grow putrid, every one knows what 

 dreadful miasmata exhale from them, and taint the air we 

 breathe. But no sooner does life depart from the body of 

 any creature, at least of any which from its size is likely to 

 become a nuisance, than myriads of different sorts of insects 

 attack it, and in various ways. First come the Histers, and 

 pierce the skin. Next follow the flesh-flies, some, that no 

 time may be lost (as Sarcophaga carnaria, &c.), depositing 

 upon it their young already hatched ; others {Musca Ccesar, 

 &c.) covering it with millions of eggs, whence in a day or 

 two proceed innumerable devourers. An idea of the dispatch 

 made by these gourmands may be gained from the combined 

 consideration of their numbers, voracity, and rapid develop- 

 ment. One female of *S'. carnaria will give birth to 20,000 

 young ; and the larvas of many flesh-flies, as Redi ascertained, 



1 According to M. Robineau Desvoidy, the dung of the badger, which is 

 placed in a separate chamber of its subterranean galleries, has its peculiar fly, 

 which he names Leria melina, the larvas of which there feed upon it ; and the 

 parent flies never ascend to the surface, but constantly reside in this dark and 

 damp abode, and can only be obtained by digging into it. Another fly, his 

 Thelida vespertilionea, in like manner, lives in the larva state on the dung of bats 

 deposited by them at the end of the grottoes of D'Arcy-sur-Eure more than 

 one hundred toises distant from their entrance ; and he describes a third fly, 

 Leria mustelina, which he believes to feed on the dung of the weasel, and names 

 other distinct species to which the dung of the fox, the rabbit, the water-rat, and 

 the field-mouse respectively afford subsistence. {Ann. Soc. Ent. de France, x. 

 255—260.) 



