4 
70 REPORT OF THE COMMISSIONER OF AGRICULTURE. 
Entomologist of Illinois for the year 1882 of the long account of his 
ae and experiments, and it is in such shape that we reproduce 
1t here: 
On the other hand, a much more important rdle is apparently played by certaim 
obscure parasites not previously detected. One of these is a minute bacterium (Mi- 
crococcus insectorum, Burrill) infesting the alimentary canal, closely allied to the 
Micrococcus found in the stomach and intestines of Silk-worms, and now known to 
cause some of the destructive diseases of that insect. From the fact that these 
parasites were extremely abundant in specimens from a field where the bugs were 
rapidly dying, while in those from adjacent fields there were relatively very few, it 
was considered probable that they were related to this destruction of the bugs. 
This conclusion was supported by the fact that they were more abundant in old 
bugs than in young, while the mortality referred to evidently also chiefly affected 
the older individuals. It was found easy to cultivate the bacterium artificially in 
organic infusions, but no opportunity offered to apply it to healthy insects. Until 
this experiment is made and the effects carefully studied, it must remain possi- 
ble that the coincidence noted was merely accidental and of no particular signifi- 
cance. 
Another parasite discovered is similar to that well known as a common enemy 
of the house-fly, and belongs to the.same genus(Hntomophthora.) This attacks 
both old and young Chinch-bugs, and finally imbeds their bodies in a mass of mold. 
There is some reason to believe that this was the active agent in an immense destruc- 
tion of Chinch-bugs which occurred in Northern Ilinois in 1866, as described by 
Dr. Shimer, of Mount Carroll. Evidence is adduced of the possibility of artifi- 
cially cultivating this parasite also, and applying it to the destruction of insects. 
Since the publication of this report Professor Forbes has taken up 
the study of bacterial diseases of certain other insects, but there has 
been, sofaras weare aware, no practical outcomeasyet. Thesubject, 
however, has a rather hopeful look, although we should be inclined to 
expect more from the Micrococcus than from the Hniomophthora. 
The evidence mentioned as to the possibility of artificially cultivating 
the latter is chiefly a translation of a paper by Metschnikoff in the Zo6- 
logischer Anzeiger for 1880, pp. 44-47, in which itis shown that the Rus- 
sian naturalist successfully induced the growth of the fungus, Isaria 
destructor, which had destroyed the celebrated Anisoplia austriaca, a 
grain pest in Russia, in beer mash. Successful attempts were made to 
infest healthy larvee with green spores taken from diseased larvee found 
in the fields, but no mention is made of success or even of experi- 
ment with the only practical substance, the beer-mash culture. 
Professor Riley has always doubted the possibility of any practical 
success in this direction, and has pointed out the difficulties in the way. 
(See American Naturalist, November, 1883, p. 1170.) 
In the introduction of the Fourth Report of the U. 8. Entomological 
Commission (LX X XV) he makes use of the following language: 
In treating of the use of yeast ferment or other fungus germs we have used essen- 
tially the language of the first edition. Time has only served to confirm us in our 
opinion of their practical futility in the field. The question of the practical use of 
these micro-organisms—these disease gernis—as insecticides is a very fascinating one, 
and is much written about just now; but unfortunately it proves most alluring to 
those who have had the least practical experience in coping with injurious insects in 
the field, and is much more apt to assume importance to the closet theorists than to 
those who, from experience, are conscious of the difficulties involved in its applica- 
bility. 
It will be appropos to quote Professor Forbes’ latest utterance upon 
this point. He says: 
Finally, the artificial cultivation of the germs of the contagious diseases of the chinch 
bug, with a view to spreading these diseases at will by means of such artificial cult- 
ure. This is a theoretical remedy only, and much additional study and experiment 
will be required to put it on a practical basis. 
