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of the pest from Virginia last year, accompanied with requests for 

 the disease, but from the weather conditions he felt warranted in 

 replying to these inquiries that the heavy rains then prevalent would 

 probably bring about the death of the chinch bugs without artificial 

 introduction of disease, and subsequent events substantiated this belief. 

 Mr. Kirkland read the following paper: 



A NEW INSECTICIDE. 

 By A. H. Kirkland, Maiden, Mass. 



To no phase of the work of exterminating the gypsy moth has more 

 careful attention been given than to the investigation of insecticides 

 that might be effectively used against this insect. The entomologist, 

 the director, and the chemists connected with the work, together with 

 the several assistants employed in experimentation, have all devoted 

 to this question their best effort, while the committee supervising the 

 work have placed all possible facilities at the disposal of those charged 

 with the investigations with a liberality that has left little to be desired. 

 Spraying with arsenicals being the chief method of combating inju- 

 rious lepidopterous larvae, the first efforts of the gypsy-moth commis- 

 sion were directed toward spraying infested trees, pursuant to the 

 recommendations of both Professors Fernald and Eiley. That Paris 

 green could not be profitably used to destroy this insect seemed at first 

 incredible, but lnanj^ careful experiments demonstrated the fact. The 

 subsequent chemical investigations by Mr. Moulton while employed by 

 the gypsy-moth committee, resulting in the discovery of arsenate of 

 lead, are familiar to all present. This insecticide, which has been used 

 exclusively in our spraying operations during the past three years, pos- 

 sesses a feature which is an aid and a hindrance at one and the same 

 time. From its insolubility it may be used in great strengths without 

 injury to the most delicate foliage, yet at the same time its effect upon 

 larvae, owing to the difficulty with which it decomposes, is not as com- 

 plete as might be desired. Numerous experiments show that great 

 strengths of arsenate of lead when used against the larger gypsy-moth 

 larvas give results hardly commensurate with the outlay, although this 

 poison is very effective when used against the smaller caterpillars at 

 the rate of from 10 to 20 pounds to 150 gallons of water. 



During the winter of 1895-96 I was enabled to spend a few weeks 

 in the botanical laboratory of the Massachusetts Agricultural College, 

 studying the effects of arsenical compounds upon vegetable tissues 

 with a view to gaining, if possible, further light concerning the cause 

 of the injury to foliage by soluble compounds of arsenic. It was found 

 that these soluble forms of arsenic transfuse by osmosis with the cell 

 contents and plasmolyze the protoplasm, thus producing the death of 

 the cells. This plasmolysis was, as might be expected, in direct ratio 

 to the solubility and quantity of the compound employed. The objec- 

 tive point of these investigations was to find out whaX cheap arsenical 



