44 
FIRST ANNUAL REPORT OF THE 
AU the Mites, however, do not feed upon living vegetable substances, like these gall- 
makers that I have just been picturing to the mind of the reader. As with the true 
Insects, many groups of them feed upon decaying substances, either of animal or vegeta¬ 
ble origin, many are Parasites, and many others are Cannibals. For example, the 
common Cheese-mite, an imported European species, feeds upon decaying cheese, 
wiiere, when it is once established, it soon multiplies with the most astonishing rapidity. 
Again: the common Itch, in that two-legged animal that Linnaeus designated as Homo 
sapiens , is caused by a microscopically minute Mite (Acarus scabiei , Linnaeus) burrowing 
under his skin, and there carrying out the great Law of Nature, “Increase and multi¬ 
ply and replenish the earth.” This species, therefore, is a true Parasite. Again : I 
have noticed many species of Mites that are what I have called “Cannibals,” haunting 
leaf-galls constructed by certain Plant-lice and Bark-lice, and feeding apparently upon 
the tender bodies of the unfortunate young lice. Galls made by other groups of insects 
they do not usually enter, because these last are invariably closed, till the gall-maker 
gnaws his way out. But galls made by Plant-lice and Bark-lice — which insects have 
no jaws at all to gnaw with, but only a beak to suck with — always burst open towards 
the latter part of their existence, so as to allow the young Lice a free exit into the 
external world. Hence into these the wandering Cannibal Mites, who are always re¬ 
markably fleet-footed in the mature state, And a ready entrance, and often carry death 
and desolation into what was before the happy home of a flourishing colony of Lice. 
“Eat and be eaten ; kill and be killed.” Everywhere this is the great universal Law of 
Nature. 
Of these Cannibal Mites, I have discovered that there is at least one species, and per¬ 
haps more than one, that preys most extensively upon the eggs of the Oyster-shell Bark- 
louse ; insomuch that upon a particular apple-twig infested by these Bark-lice I have 
found, on lifting and carefully examining six hundred scales about the last of October, 
that at least two-tliirds of the whole number were either already gutted, or were under¬ 
going the process of being gutted, by the minute larvse of a Mite.* What I believe, 
though I am not absolutely certain, to be the eggs of this Mite are deposited here and 
there upon the bark among the scales, in little patches of six or eight, and are exceed¬ 
ingly minute, smooth, shining, perfectly globular bodies, rather less in diameter than 
the transverse diameter of the egg of the oyster-sliell Bark-louse. Most of them are 
blood-red, but some, which appear to be the empty shells of such as have already 
hatched out, are transparent and colorless. Repeatedly, on raising the Bark-louse 
scales both in the autumn and in the early spring months, I have found from one to 
eight of the larvae of some kind of Mite — whether hatched out or not from the above- 
mentioned eggs is not perfectly clear— interspersed among the eggs of the Bark-louse. 
In some of these cases the eggs of the Bark-louse were sound and untouched ; in others 
there were only a few of them sucked dry and shriveled up ; in others again, at one end 
of the scale the eggs would be sucked dry and at the other end perfectly plump and 
* During my attendance at the inauguration of the Horticultural Society of Northern Illinois, at Mt. 
Car-roll, Dec. 18th-20th, 1867, and before I had said a word there about these Cannibal Mites, but after 
the whole of this chapter was in the hands of the printer, I was much gratified by hearing Dr. H. 
Shimer, of Mt. Carrol, inform the meeting that he had himself discovered that the imported Bark-louse 
was preyed on quite extensively by a species of Mite (Acarus.) Thus, as often happens, the same dis¬ 
covery has been made at the same time, by two independent observers. Of course, Dr. Shimer’s evidence 
is cumulative proof, if any be needed by any one, of the reality of the discovery. — Dec. 21,1867. 
