TRANSACTIONS OF NORTHERN ILL. HORTICULTURAL SOCIETY. 333 



separate, distinct head and abdomen, and, as a rule, have eight legs — the 

 normal number of legs to a true insect being six, yet some true mites 

 have only six legs). They were so small, and so near the color of the 

 leaf, that even with the high power of the glass, they could hardly be 

 seen, except when in motion, yet they produced a more perceptible 

 wound on the leaf than the so very much larger lice ; they destroyed 

 entirely the under cuticle of the leaf each way from a central point. These 

 mites feed under an exceeding firre web, spun by them, perhaps, for pro- 

 tection against unwholesome weather and their natural enemies. Though 

 I have been looking up the mite family somewhat for the past four years, 

 these appeared to be a species I had not before observed ; I therefore 

 proceeded to give them the closest scrutiny. While doing so, there was 

 a sudden motion, and one of the largest was captured and raised up in 

 air, struggled a moment, and disappeared. At first I could see nothing 

 to produce this effect, but by a little change of light, I made out the out- 

 line of a slender, pellucid, worm-like larvae, flattened out on the leaf. 

 On watching it a few moments, it captured another mite ; it appeared to 

 suck the little creature into its capacious maw bodily, not puncturing and 

 sucking out its juices as predaceous larvae usually do. On examination 

 of other leaves from the same tree, I found colonies of mites on nearly 

 all, and in nearly every one, one or more of their immense (when com- 

 pared to them) enemies. The little fellows would caper over and around 

 the glutinous creatures until their turn came, when down they would go. 

 A continued search showed this larvae matured and in its pupa case, the 

 dark outline of the future gnat showing through the transparent case 

 plainly enough for me to determine that a brilliant, jet black, quick- 

 motioned, mere point of a gnat, observed flitting among the leaves, was 

 the parent of the mites' deadly foe. I jot down these notes to call the 

 reader's attention more plainly to cause and effect in the diseases of trees 

 and plants ; for instance, after the weather has been dry and hot for a 

 considerable length of time, we see many trees and plants showing sickly, 

 yellow foliage. This is, as a rule, attributed to, by nearly all, the great 

 heat and drought solely. They are certainly the primal causes, for these 

 smaller and more delicate noxious things can only breed fast enough to 

 become noxious during such periods, but the plants would get along well 

 enough \{ they would only let them alone. In this Cottonwood leaf, for 

 instance, the weather being right, the aphides breed exceedingly fast, and 

 puncture the leaves; the weather being favorable, and the location of this tree 

 being very suitable, fungi attack these punctures and destroy the vitality of 

 the leaf, and it falls to the ground. The aphides, as well as the fungi, have 

 their enemies at hand ; but the conditions are, perhaps, not so favorable 

 for their generation as for the two primaries ; and further, aphides, mites 

 and fungi propagate so enormously fast under the most favoring condi- 

 tions of food and weather, as to be beyond the power of their most potent 

 enemies to check. Yet how nicely all are balanced; strike out of exist- 

 ence a few, only a few, of God's most insignificant creatures, selected 

 from the insignificant gnats, and then let a region be visited with three 

 months of heat and drought and other right conditions, and every, or 



