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Somewhat more than twenty years ago the lower forms of some fungi attracted the 

 attention of many students, and especially of Dr. Bail, of Prussia. The reports of his 

 observations are scattered in different periodicals, and the final result of my study of 

 those reports was the conviction that a remedy for insect pests, offering several promi- 

 nent advantages, could be found in the easy application of the yeast fungus. Further, 

 that this remedy could be used probably against the famous Colorado grasshopper, for 

 the destruction of which the Government has appointed a commission appropriated with 

 $75,000 ; also, that the remedy could be tried in an easy way against the obnoxious 

 hairy caterpillars, against the potato bugs, and last, but not least, in every greenhouse 

 against leaf lice and similar pests. 



Dr. Bail asserts that he has proved by many skilful 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 mould not easy to be removed. The second is the common mould, 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 mould, and that the seeds of mould are transformed 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 

 repeat 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 propositicn, as Dr. Bail 

 has proved that mould 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 1861, which were 

 illustrated by the exhibition of mould 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 

 haked with this yeast. Both productions were declared perfect by all who tasted them 

 — an experiment in which I did not feel obliged myself to join, as both are to be had 

 prepared without the fungus of the house-fly. 



In a later communication Dr. Bail states that the use of mould has been the secret 

 in brewing formerly certain kinds of a strong and well-reputed beer. 



For the so-called jopenbier in Danzig the mash was not used before the forests of 

 mould grown on its surface had sunk to the bottom — or, in other words, till the spores 

 of the mould were sown by themselves on the mash. 



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 insects, 

 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 oculist'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 microscope proved to be 

 filled with spores of fungus. 



More to the point are epizootics produced by this fungus and observed on insects in 

 the open air. 



A really pestilential epizootic of the common dung-fly was observed in 1867. Not 

 only those, but many other insects, died in the same locality and in the same manner; 

 also other species of flies and gnats, the caterpillars of moths and of Phal^nids, and 

 the common hairy caterpillars of a moth which is very nearly related to the famous 

 hairy caterpillar of the Boston Common. Of some species the destruction was so com- 

 plete that the next year they were very rare. During those years the caterpillars of 



