Nov., 1910.] ANNUAL REPORTS. 45 



These experiments were under the immediate direction of Prof E. D. San- 

 derson. They weir brought to a close this pasl Beason. 



A part of the data secured have already been summarized and published 

 as Scientific Contributions l and l of this station. 



INVESTIGATIONS UNDER THE HATCH FUND. 

 The Black Fly. 



Experiments were conducted in the summer of 1909 looking toward some 

 means of control of the black flies or "buffalo gnats" in the summer resort 

 regions of New Eampshire, particularly in the AN lute Mountains. The place 

 chosen for this work was the town of Randolph, and the streams treated 

 were the Moose River and some of its tributaries. 



The treatment consisted of the application of a soluble oil known as "Phino- 

 tas Oil" to these streams. This oil, mixing readily with the water, came into 

 contact with the larvae of the black fly attached to stones under the surface 

 of the water, and killed them. 



The serious difficulty in this treatment lay in the possible injury to trout, 

 but an experiment of the summer of 1909 seemed to indicate that this danger 

 might be avoided by using nets stretched across the stream to turn the fish 

 back and prevent them from descending the stream with the oil and thus 

 remaining too long in it. 



In May and June of the past year, 1910, further experiments were per- 

 formed in the same streams. It was desired to establish definitely the dosage 

 necessary to kill the black fly larva?, and to determine whether the fish might 

 be entirely protected from injury. 



The experiment was successful. The proper dosage and duration of treat- 

 ment were ascertained, and it was demonstrated that with proper precautions 

 this treatment can be safely and economically applied. A section of stream 

 was so treated, with the result that practically all larva? were exterminated, 

 and no fish were injured. 



The Antlered Maple Worm. 



In the summer of 1909 the so-called Antlered Maple Worm, Heterocampa 

 gutivitta, was under observation and study by this department. A serious 

 outbreak of this pest in 1908 had defoliated the hardwood through a large 

 area of the state. The outbreak was repeated in 1909. The results of this 

 department's investigations were published in full in the biennial report for 

 1906-08 



The past season, 1910, witnessed an almost complete cessation of the abnor- 

 mal numbers of this insect. Specimens were observed at various points, but 

 they were not in sufficient numbers to cause injury or comment. In one area 

 a fairly large number of the larva? were observed, but when they were still 

 small heavy storms washed them from the trees and apparently they did not 

 regain their foothold. 



The cause of the sudden reduction in numbers whether due to climatic 

 conditions, natural enemies, bacterial disease or some other adverse circum- 

 stance is not known. However oscillations of this nature are not at all 

 uncommon and in the case of this insect the sudden cessation noted was not 

 surprising. 



