188 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
YEAST FERMENT : FUNGUS INFECTION. 
The fact that insects, like other animals, are subject to diseases of an 
epidemic nature and of a fungus origin has led some persons to hope 
and believe that the germs of destruction could be, so to speak, arti- 
ficially sown among those which it was desired to destroy. Dr. J. L. 
LeConte, of Philadelphia, was the first in this country, so far as we are 
aware, to suggest the introduction and communication of such diseases 
at pleasure for the destruction of insect pests, in a paper read at the 
Portland (1874) meeting of the Association for the Ad van cement of Sci- 
ence. Dr. H. A. Hagen, of Cambridge, Mass., has elaborated the idea, 
and strongly recommended as a general insecticide the use of beer- 
mash, or diluted yeast, applied with a syringe or a sprinkler. We quote 
the following somewhat sanguine words from an article which he pub- 
lished in Canadian Entomologist (vol. xi, June, 1879) : 
Dr. Bail asserts that he has proved by many skillful experiments that four species 
of microscopical fungi are merely different developments of the same species. One of 
them, the fungus of the common house-fly, is the vexation of every housekeeper. The 
dead flies stick in the fall firmly to the windows, or anywhere else, and are covered 
by a white mold not easy to be removed. The second is the common mold, known to 
everybody, and easily to be produced on vegetable matter in a damp place. The 
third is the yeast fungus, a microscopical species, and the basis of the work done by 
yeast of fermentation. The fourth is a small water-plant, known only to professional 
botanists. Dr. Bail contends that the spores of the fungus of the house-fly develop in 
water in this last species, out of water in mold, and that the seeds of mold are trans- 
formed in the mash-tub into yeast fungus. 
The experiments made by Dr. Bail cover a period of more than a dozen years, since 
the numerous objections which were made against; his results induced him to rejjeat 
again and again his experiments in different ways. I am obliged to state that even 
now prominent botanists do not accept Dr. Bail's views, which he maintains to be 
true and to be corroborated by new and sure experiments, This question, important 
as it may be for botanists, is without any influence regarding my proposition, as Dr. 
Bail has proved that mold sowed on mash produces fermentation and the formation 
of a yeast fungus, which kills insects as well as the fungus of the house-fly. I was 
present at the lectures of Dr. Bail before the association of naturalists, in 1801, which 
were illustrated by the exhibition of mold grown on mash on which the fungus of the 
house-fly had been sown, and by a keg of beer brewed from such mash, and by a cake 
baked with this yeast. 
* # # * * # # 
Dr. Bail has proved by numerous experiments that healthy insects brought in con- 
tact with mash and fed with it are directly infested by the spores of the fungus with 
fatal consequence. These facts, not belonging strictly to the main part of his experi- 
ments, were observed first by chance and later on purpose. The most different in- 
sects, flies, mosquitoes, caterpillars, showed all the same results. The experiments 
were made in such a delicate manner that a small drop of blood taken with an ocu- 
list's needle from the abdomen of a house-fly left the animal so far intact that the same 
operation could be repeated in two days again. Both drops examined with the mi- 
croscope proved to bo filled with spores of fungus. 
# # # * # # # 
Considering those facts, which are doubtless true, and considering the easy way 
in which the poisonoilB fungus can always and everywhere bo procured and adhibited, 
I believe that I should be justified in proposing to make a trial of it against insect 
