PROCEEDINGS, 1916. 5T 



small lots of larvae belonging to any one species. This article is a brief preliminary ac- 

 count of one aspect of this work, compiled from the notes taken during the past season. 

 The following is a list of the materials used in the experiments, whether in combina- 

 tion or alone.: 



Bordeaux — 4-4-40 formula. 



Lime Sulphur — 1.009 sp. gr. 



Barium tetrasulphide (B.T.S.) — 2| lbs. to 40 gals., when used alone; 21bs. to 40 

 when combined with soluble sulphur. 



Sodium sulphide (soluble sulphur) — 1 lb. to 40 gals. 



Barium tetrasulphide and soluble sulphur — Barium tetrasulphide, 2 lbs. to 40 gale.; 

 Sodium sulphide (soluble sulphur) | lb. to 40 gals. 



Arsenate of lime (dry) 44 per cent AS2O5) — § lb. to 40 gals. 



Barium arsenate (dry) — 1 lb. to 40 gals. 



Neutral (triplumbic) lead arsenate (dry> — 1J lbs. to 40 gals. 



Acid lead arsenate (dry) — 1 lb. to 40 gals. 



Sodium arsenate (crystals) — 4-5 lb. to 40 gals. 



Arsenite of zinc — 1 lb. to 40 gals. 



The poisons and fungicides in the strengths indicated were fed to nine separate lots 

 of larvae as shown in tables 2 to 10. Twenty-five larvae of some species and ten of oth- 

 ers were used in each tray, and for the sake of uniformity all results have been reduced 

 to a percentage basis. Daily notes were taken regarding the action of each poison and 

 each combination. For convenience in tabulating, however, and in order to show the 

 comparative killing values of the various combinations in the clearest way, the tables 

 are arranged to show the effect of each over a period of days. The length of the period 

 chosen depends upon the time at which the effect of the different mixtures is most con- 

 spicuous. It was found, when the work was completed, that certain species were almost 

 entirely killed, while others fed for the same period on the same poisons without appar- 

 ent effect. 



All the feeding was done in Fiske trays, the food being kept green by inserting the 

 stems through perforations in the corks of crook-necked vials containing water. The 

 leaves were, as far as possible, gathered from the same trees, so as to present a uniform 

 surface for the poison to adhere. The leaves were wet by dipping them once into the 

 well agitated spray solution and drying before feeding. 



Tables No. 2 to 10 show the percentage of larvae dead at the end of the period when 

 a comparison of the various poisons used showed their effect most clearly. 



