62 TKANSACTIONS OF THE ILLINOIS 



pillars becoming butterflies, and how suddenly myriads of noxious insects 

 can be swept out of existence by an enemy. 



I once noticed a field forty rods long by twenty wide, covered very 

 thickly by a common weed, the heads of which at one end of the field 

 showed a bright oraAge color, which died out gradually at the middle, 

 and farther on towards the south end a dark shade appeared, which soon 

 became black, but quickly gave place to the proper color of the weed, 

 which extended unbroken over the south end of the field. This strange 

 coloration attracted my attention, and I determined to investigate the 

 cause. Commencing at the north end, I found the bright orange to be 

 caused by the pupa-cases of the larvae of one of our largest lady-birds 

 (probably coccinella novemnotafa) ; farther in the cases were still occupied 

 by the pupae. A little farther the larvae were affixing themselves to the 

 extreme tips of the weeds to undergo their transformations. ■ A little 

 farther in and thousands of beetles were emerging from these cases. 



And here commenced a field of slaughter long to be remembered; 

 more lives were being taken each hour than of human lives during the 

 whole of our great rebellion. The weeds grew as thickly as possible, and 

 were luxuriant. The lady-birds had been attracted at the north end of 

 the field by a large, black plant-louse, which had spread, generation after 

 generation, in serried ranks of millions, towards the south, sucking the 

 life from the weeds as they passed. They had been discovered by the 

 lady-birds and their eggs were deposited among them, which soon hatched 

 and let loose among the tender plant-lice the gluttonous, tiger-like 

 destroyers ; but the plant-lice had advanced in their march of destruction 

 considerably while the lady-bird eggs were hatching, and the destroyer 

 did not obliterate them until they had destroyed the weeds for more than 

 twenty rods. 



From this example we can learn some lessons : In the first place, 

 we see how wonderfully fast two kinds of life can multiply when all things 

 are favorable ; secondljj, how quickly one species can destroy and be 

 destroyed ; and, thirdly, how the irruption of a noxious insect, though it 

 may do us serious harm at the time, may ultimately prove to our great 

 advantage, in this way, by furnishing food in plenty for some very beneficial 

 insect, thereby increasing its numbers to such an extent as to be of great 

 service in destroying other noxious insects; for most insectivorous insects 

 feed indiscriminately on several species. The coming among us of the 

 Colorado potato-beetle made great and lasting changes in our insect-life, 

 many of which are in our favor. I have watched and studied these 

 changes with great pleasure. The coming among us of this one species 

 probably produced as great a convulsion in all life as we shall ever see 

 produced in a natural way ; for there is scarcely any life, vegetable or 

 animal, in this State, that has not in some way been affected by its intro- 

 duction, and before Nature had reached her proper balance from its intro- 

 duction we meet with another visitor, obliterating another of our valued 

 products in its devouring march, in the shape of the cabbage-worm {Fieris 

 rupee), and our efforts to destroy it and save our cabbages are as inef- 

 fectual as our first battles with the potato-bugs, and will continue to be 



