36 TRANSACTIONS OF THE ILLINOIS 



and that the bacteria producing it may be preserved without loss of 

 effectiveness over at least one year, — requiring in fact no particular 

 preparation or care to that end. It would therefore be sufficient for 

 my present purpose to show that the affection of our native cater- 

 pillars, which I shall presently describe, is really identical in its 

 essential characters with that above discussed; since this would justify 

 us in applying these conclusions to the disease as shown in our cab- 

 bage-worm and apple-tree caterpillar; but not content with this, I 

 have made some additional experiments for the purpose of putting 

 these conclusions on an independent basis. 



I can report here only a small part of the studies which I have 

 made, and shall content myself with a description of the disease as 

 it appeared in the European cabbage-worm this fall, and of some 

 experimental results obtained in studying it in this insect and in the 

 yellow-necked apple caterpillar (Datana ministra). 



I suppose that many of you, at least of those living in the 

 northern and eastern part of State, must have noticed with surprise 

 the curious fate which overtook a large percentage of the cabbage- 

 worms of nearly every field this fall. Hundreds of the bodies of 

 these pests were to be seen rotting on the cabbage leaves, or dried to 

 a shrunken, blackened remnant, often twenty or thirty to a single 

 head at once. 



Among those with whom I have talked about the matter, all 

 sorts of hypotheses were prevalent. Some supposed that the season 

 had been too wet for the worms; others, that the weather had been 

 too dry. Some explained the difficulty as due to unusual heat, and 

 others, as clearly a consequence of unusual cold; while still others 

 looked upon it as conclusive evidence that the lime or salt or ashes 

 or what-not with which they had sprinkled their cabbages, had taken 

 effect, and was, after all, the remedy of remedies for cabbage-worms. 

 ' This cabbage-worm plague was quite unevenly distributed; some 

 small and isolated fields not exhibiting a trace of it, while others but 

 a little way distant, were fairly reeking with death and decay. It 

 increased in severity with the advance of the season, until in the 

 latter part of October and in November it was a rare thing in my 

 vicinity to see a healthy chrysalis. Nearly every worm perished 

 before maturity. 



It seems also to have progressed from the east westward, not 

 appearing in Fulton and Stark Counties until some weeks after we 

 noted it here, and not reaching Iowa at all, as far as I have been 

 able to learn. 



On the other hand it was barely remarked near Washington 

 three years ago, although no particular attention was paid to it. It 

 certainly was not abroad here last year, as we were carefully experi- 

 menting upon the cabl)age worm all the autumn, both in the field 

 and. the laboratory, and could not possiblv jhf^ve failed to detect it. 



