REPORT OF THE ENTOMOLOGIST. 261 



on account of their great numbers, the insects were carefully removed 

 from all but a few leaves, and those allowed to remain were numbered. 

 Yeast in i»n active state of fermentation and from several makers was 

 then applied so as to drench the insects and all parts of the plants; and 

 in some cases oj^en vessels filled with yeast were i)laced below the plants. 

 In some cases the foliai^e of the plants was found much disfigured by 

 brownish blotches, ai>])arently caused by the yeast. Sometimes the in- 

 sects multiplied rapidly after the application of the fungus, and a very 

 few which died were not found to contain the spores or mycelium of 

 fungi so far as could be seen by a careful examination with high powers 

 of the microscope, and, indeed, this may be given as the general residt 

 of the experiments earned on where the humidity of the air was not ex- 

 cessive. At other times the aphides died in considerable numbers ; and, 

 when placed oii pieces of moist earthenware, the dead insects devel- 

 oped quantities of hyphae, which were recognized by their fruit as be- 

 longing to one of the molds {Miicor sp.) This result is especially 

 noticeable in an experiment (No. 5) in which the plant was i)laced in 

 a close Wardian case, where the moisture alone might have caused 

 the death of the insects, and where the torulae, covering everything, 

 would naturally tend to assume the mucor form, and the ever present 

 spores of molds to develop mycelium and this fruit. A test experiment 

 (No. 9) in which aphides not subjected to the yeast treatment became 

 covered by a fruiting mucor goes to show that too much credit must no* 

 be given to the yeast as the caii«e of the death. 



From his experiments Professor Prentiss concludes that yeast cannot 

 be regarded as a reliable remedy against such insects as commonly affect 

 plants cultivated in green-houses, rooms, and parlors, while it may injure 

 some plants by disfiguring their foliage and giving rise to m-olds on the 

 jars and soil in which they are grown ; but the fact that some insects are 

 subject to fungoid epizootics renders it possible that we may yet be able 

 to induce diseases of this nature at will. 



While, therefore, the practical ap])lication of fungi as insecticides is 

 as yet far from being an assured success, and climatic conditions must, 

 necessarily, be always carefully considered in applying remedies of this 

 nature, even after it is den)onstrated that they can be successfully ap- 

 plied under the most favorable conditions, yet we believe that the sub- 

 ject is worthy of much careful study and exi)erimentation, especially 

 with a view to cultivating destructive fungi in Pasteur's fluid, sweet- 

 ened paste, and other substances known to be favorable to the growth 

 of the seorganisms, in which they may be extensively i)roi»agated, and 

 with whicl! they may be readily applied to plants infested with the in- 

 sects it is desiiable to destroy. 



