June, 1919] ANNUAL REPORTS. 25 



facts of interest. Through the fall and winter of 1917-18 laboratory experi- 

 ments were carried out by a co-operative arrangement, whereby Mr. C. A. 

 Weigel, representing the Department, was afforded facihties in the laboratory 

 of the Ohio State University. 



The subjects studied in the course of the field work of this investigation 

 included the following: 



(a) The relation of the position of the larva within its mine to its reaction 

 to contact insecticides, apphed to the sm-face of the leaf tissue. 



(b) The relation of the age of the miner to its reaction to such insecticides. 



(c) The mortahty of the miner in its egg stage to the application of similar 

 insecticides. 



(d) MortaUty of the miner in its pupal stage within the mine when contact 

 insecticides are applied to the siu-face of the leaf tissue. 



(e) The relation of varying strengths of contact insecticides to the above 

 reactions. 



(f) The general facts covering the penetration of contact insecticides into 

 the cavity made by leaf miners. 



(g) The residual effects of insecticidal application on the succeeding genera- 

 tion of the apple leaf miner. 



In addition to the above investigation a brief study was made of the reaction 

 of the quince leaf miner under similar conditions. Life history studies of 

 the apple leaf miner were carried out in connection with the investigation. 

 The entire study has yielded results of scientific value and interest. These 

 results will soon be prepared for publication. 



Control of Black Flies. 



Each season's additional work in control of black flies discloses new phases 

 of the subject which should be studied. The work begun last year and pro- 

 jected for the coming season is intended to disclose the distribution and 

 abundance of various species of black flies in different mountain areas of New 

 Hampshire and at varying times of the year. With this in view collections of 

 larvae are being made at numerous points and records taken as to the relative 

 abundance of the several species in their larval stage. 



Insect Record. 



The Department maintains, as in former years, a careful cross index, show- 

 ing the distribution of injiu-ious insects in New Hampshire, their food plants 

 and other data. 



The Insecticidal Properties of Hellebore. 



A new project, the Insecticidal Properties of Hellebore, has been outlined and 

 mvestigations will be carried out during the coming summer. This project 

 is intended to be carried along at the same time with the current season's 

 study of pyrethrum, the latter being a part of the Adams Fund Project, Con- 

 trol of Root Maggots by Insecticides. 



We propose to carry out inquiry concerning the following properties of 

 powdered hellebore as commonly used and recommended for the control of 



