The third squadron is attracted when the fat begins to undergo an acid fermentation. These consist of coleoptera and lepidoptera, beetles and butterflies, and among them is Dermestes Lardarius, the Bacon Beetle.
When the fats become cheesy the diptera reappear, and among them is Pyophila Casei, the fly which breeds jumpers in cheese, which is accompanied by a beetle, whose larvæ are connoisseurs in rancidity.
When the carcase becomes ammoniacal, black, and slimy, it is visited by a fifth squadron of flies and beetles.
And these are succeeded by the sixth squadron, consisting of acari or mites, whose function it is to dry up the moisture and reduce the carcase to a mummy-like condition.
The dried carcase proves attractive to the seventh squadron, consisting of beetles and moths, some of which are the familiar pests of the housewife, the furrier, and the keepers of museums. These animals gnaw the softer parts, such as ligaments, and leave nothing but a fine powder behind them, which is in fact their dung.
The last and eighth squadron consists solely of beetles, which clean up the débris, in the shape of dung, shells, pupa cases, &c., of the seven squadrons which have preceded them.
M. Mégnin, being an entomologist and not a bacteriologist, deals exclusively with the insects concerned in making away with a carcase, but it is evident that bacteria work hand in hand with them.
There are many other instances which may be quoted of the co-operation of fungi with other organisms, and it is only of late years that we have appreciated the fact of symbiosis, or the living together of two organisms for the mutual benefit of each. This fact was first pointed out in so-called lichens, which are now shown to be complex bodies consisting of a fungus and an alga, living in symbiotic community for the mutual benefit of each.
It was next shown that the papilionaceous leguminosæ are unable to flourish without certain bacterial nodules which grow upon their roots, and by the instrumentality of which they can appropriate the nitrogen of the air, and thus the fact, familiar for centuries, that the leguminosæ leave the ground in a state of great fertility, while they are singularly independent of nitrogenous manures, has been explained.