February, '16] ENTOMOLOGISTS' DISCUSSIONS 89 



the berry patch in the fall of the year or late summer and at that time 

 they feed on the leaves of the plants. 



I would like to ask Dr. Headlee a question. Did the sulphur and 

 arsenic act as a repellent? 



Mr. T. J. Headlee: Purely as a repellent. Very few cases of 

 destroying the weevils. 



]\Ir. William INIoore: We find that the weevils do not feed in the 

 spring. 



President Glenn W. Herrick: We will now Hsten to a paper by 

 Mr. C. L. Metcalf. 



THE EFFECT OF CONTACT INSECTICIDES ON THE 

 LARV^ OF SYRPHID^ 



By C. L. Metcalf, Columbus, Ohio 

 (Withdrawn for publication elsewhere) 



President Glenn W. Herrick: I am interested in the use and 

 effect of black-leaf 40 because it is widely used in New York State for 

 controlling aphis on apple. 



Secretary A. F, Burgess: I would hke to ask in regard to the 

 method of spraying in your experiment. 



Mr. C. L. Metcalf: The tests, except one, were laboratory tests 

 in which a small part of the twig was cut off and this twig and the 

 aphids and larvae present, after being sprayed with the solution, were 

 placed in a cheese-cloth covered glass jar. 



In the last experiment a section of a limb of a sycamore tree about 

 three feet long was isolated with a band of tree tanglefoot at each end 

 so the larva could not escape and the insecticide applied in the field. 



Secretary A. F. Burgess: Have these experiments been checked 

 in the field to determine the effect of the different solutions you used? 

 The solutions you used were no doubt weak. The contact solutions 

 that are being used in the field at the present time have to be strong. 

 The sample can be sprayed with a weak solution but when it comes to 

 field applications it is more difficult to do effective work with weak 

 solutions. 



Mr. C. L. Metcalf: The black-leaf 40 was used at the strength 

 recommended for destroying ordinarily resistant plant lice. In the 

 other cases the question to be determined is whether in the long run it 

 ■v\ill be more satisfactory to use a stronger solution, thus killing 

 aphids and larvae; or a weaker solution which would allow the 

 larvae to remain and destroy any aphids not covered, and so not 

 killed by the insecticide. 



