STATE HORTICULTURAL SOCIETY. 



63 



SO. But Nature will give us a Nemesis in the shape of some tiny, insig- 

 nificant little insect, before which the cabbage-worm will disappear like 

 the white frost before the morning sun ; yet we will always be troubled 

 somewhat by these two pests ; but as soon as Nature regains her balance 

 they will be held in subjection, so as to be only occasionally noxious, like 

 the plant-lice before mentioned, which left their enemies behind at the 

 start, but will be overtaken and destroyed ; and their introduction may 

 prove to be to our ultimate benefit. 



There are numerous species of insects whose young would destroy 

 utterly, in one or more seasons, their proper food-plants were their 

 enemies stricken from existence. And the converse is true of these 

 enemies. The chances for a caterpillar to reach maturity in the shape of 

 a butterfly or moth are exceedingly few ; its deadly enemies are ever on 

 the alert to place their eggs on its unprotected back, or to sink them in 

 its vitals, or to carry it off bodily as food for their unhatched young. I 

 once found feeding near together two of our largest caterpillars, those of 

 the moth Attacus cecropia. On the back of one were glued eighty-two 

 tiny eggs, on that of the other eighty-four, and from nearly every one of 

 these eggs a little maggot would hatch which would burrow its way 

 through the living tissue of the caterpillar and prey upon his substance 

 to his certain destruction. If we observe carefully we will find that 

 nearly every kind of life has its deadly foes, and is kept by them in 

 complete subjection generally, so as not to become so numerous as to, 

 for any length of time, occupy more than their share of space to the 

 detriment of other life. 



The great fluctuations in insect-life as regards numbers, often to our 

 misfortune, have their origin in causes that can generally be easily traced, 

 but are sometimes obscure. The more prominent of these causes are : 

 Firstly, the almost complete destruction of a species by an enemy that 

 feeds entirely on it. When the food is gone the enemy in that region 

 all starve ; the few left of the other, being relieved of this particular 

 enemy, soon swarm in countless myriads (and may so increase in this 

 way unchecked as to devour all its proper food within its reach and the 

 whole brood starve to death before maturity, as I have seen chinch-bugs 

 and locusts (grasshoppers) do); but its natural enemy attacks it on all 

 plants, and again sweeps it from the face of our fair fields, and if all 

 things are propitious destroys it so completely that again it must starve; 

 and secondly, by climatic changes, destroying the eaten or the eater; or 

 thirdly, from the one or the other being destroyed by disease, for insects 

 are subject to disease the same as all other life. A notable example of 

 the power of disease over insect-life will be recollected by many present, 

 that happened about fifteen years ago, when by far the largest brood of 

 chinch-bugs Illinois has ever known was almost entirely annihilated over 

 the length and breadth of the State by disease, between two Sundays. 

 By careful search hardly a specimen could be found for the cabinet the 

 following season. 



Had I time I would like to say something of the many (though not 

 always unreasonable) mistakes made by the unobserving when they think 



