268 Illinois State Lahoratoi^y of Natural History. 



ing the progress of a series of experiments with insecticides 

 upon the cabbage worm, and that nothing of the sort was seen 

 by us. 



When first noticed there, its distribution was peculiarly 

 irregular. In certain small fields, for example, not one half 

 mile distant from those in which the disease was raging 

 violently, affecting one fourth to one half of the worms in 

 sight, not a single dead larva could be found by very careful 

 search. A few weeks later (October 4), larvae in these fields 

 were suffering as severely as the others, 20 per cent, of the 

 worms, 'on an average, showing signs of illness. 



September 27, at Rosehill, near Chicago, I visited fields in 

 which, although the worms were fairly abundant, I could not 

 find a single diseased larva during a careful examination 

 of more than a hundred individuals ; while across a road 

 and a half mile away, the disease was fully at work in four 

 adjacent fields, and fully one fourth of the worms had been 

 attacked. These were in all stages of the disease, many of 

 them being dead and rotten. The identity of the affection 

 with that observed at Normal was established by careful micro- 

 scopic examination. 



From correspondents to whom I had described the cabbage 

 worm mortality at Normal, I received various reports. Prof. 

 A. J. Cook, of the State Agricultural College of Michigan, wrote 

 me, October 2, that about 10 per cent, of the cabbage worms 

 near Lansing were affected by it. On the other hand. Prof, 

 Lintner, State Entomologist of New York, informed me, No- 

 vember 3, that it had not been noticed with him. Dr. E. R. 

 Boardman, in Stark county, sixty miles northwest of Normal, 

 reported, September 29, that the cabbage worm was there very 

 destructive, but that no appearance of the disease in question 

 was discoverable. October 5 he repeated this observation, but 

 on the 13th of that month he finally found a very few affected 

 larvge. 



D. S. Harris, of Cuba, in Fulton county, nearly south of 

 Dr. Boardman, first wrote me on the 13th of October that no 

 disease had appeared among the cabbage worms about his place, 

 nor at adjacent towns, as he had learned by careful search and 

 inquiry, but on the 25th of the month he wrote; " That disease 



