22 
The first actual experimental operations on this subject in Amer¬ 
ica were based, unfortunately, upon the mistaken ideas of Bail 
with respect to the interchangeable relations of the common house¬ 
fly fungus, the common molds, the yeast plant, and the fish fungus 
(Saprolegnia), which DeBary referred to in 1884 as a “subject 
for the history of botanical error.” In 1879, Dr. H. A. Hagen, 
Curator of Entomology to the Museum of Comparative Zoology 
at Cambridge, Mass., began to write on the use cf yeast as an 
insecticide, upon the supposition that insect diseases might thus 
be provoked through a transformation of the yeast plant into a 
parasitic fungus. This theory broke down, however, under the prac¬ 
tical tests made by Hagen himself, and by Biley, Prentiss, Smith, 
Cook, Willet, and others, during the years 1879 to 1882; but obser¬ 
vation of insect disease was evidently stimulated by the general 
attention which the discussion of Hagen’s article attracted, and a 
number of scattered notes of miscellaneous observations published 
during the years next following will be found included in the 
bibliographical list appended to this paper. As none of these minor 
observations have thus far led to practical experiments, they 
need not be further discussed in this place. 
The only experimental work with the fungi of insect disease 
since done in this country has grown out of studies of the flaclierie of 
caterpillars, especially of the common cabbage worm (Pieris rapes), 
and of three species of fungous parasites of the chinch-bug—all first 
distinguished as parasites of that insect and all first extensively studied 
in that relation by the writer at the Illinois State Laboratory of 
Natural History. The cabbage-'worm disease, which I have since 
identified with flachcrie, was first noticed in this country by Biley 
and his assistants at Washington,* and reported by him in 1880, 
although not recognized at the time as a contagious malady. It 
did not appear in Illinois until the fall of 1883, at which time I 
began my investigation of it, making studies of the disease in the 
cabbage worm itself, cultures of bacteria from the alimentary 
canal and body-fluids of sick larvae, and attempts to convey the 
disease to distant points by sending dead and diseased caterpillars 
as an infection material.f Similar studies were made by me in 
1883 and 1884 of flacherie of the apple and walnut caterpillars 
(Daiana ministra and D. cmgusi), infection experiments in these 
cases being made by spraying the food of healthy larvae with fluid 
cultures of the bacteria found in those suffering from disease. 
The preliminary steps had been taken also by the writer before 
this time —that is in the fall of 1882 and 1883—towards experi¬ 
mental work with the contagious diseases of the chinch-bug. Cul¬ 
tures w r ere made of bacteria then first found in certain coecal append- 
* Evidence of the occurrence of this affection of cabbage worms in Europe will be found in the 
following statement taken from Curtis's “Farm Insects," * 1 1859, p. 96: “On the 20th [September, 1841J 
they [larva? of the ‘white cabbage-butterfly’ ! appeared healthy, but inclining rather to a yellow color; 
it rained during the night, and on looking at them in the afternoon of the following day, I saw they 
had removed to a leaf, to which they stuck by four of their hinder legs, and, to my surprise, they 
were of a dirty color, and rotten, the skins being lax, and lying just as the wind blew them about. 
I found they only contained some cream- colored fluid, a portion of which was scattered upon the 
leaves.” 
t These were the first successful experiments of which I have seen any record for the convey¬ 
ance of the diseases of injurious insects by this method of contagion, which has since come into 
very extensive use in connection with the chinch-bug. 
