1918 ENTOMOLOGICAL SOCIETY. 31 



insect have been made and investigations directed towards controlling it under 

 field conditions. 



In the spring of 1916, a special search was made for the puparia in land 

 near Ottawa which had been used for onions in 1915. On April 25th, one 

 puparium was found in the soil at a depth of 4I/2 inches. On April 28th a 

 further search was made with the following results: — 



1 puparium found at a depth of 3 inches 

 1 " '' " 3% '' 



1 " « « 43/g '' 



2 " " " 43/4 '' 

 1 " « " 47/g " 

 1 " " « 51/8 '' 

 1 " " " 53/8 '' 



1 " " « 61/8 " 



1 « " " 63/g <' 



Altogether on the above two days, 11 healthy puparia were found at depths 

 in the soil ranging from three inches to six and three-eighths inches. In addi- 

 tion other puparia were collected but as these were within five inches of the 

 surface, the exact depths were not noted. A close watch for larvae was kept 

 but none were observed. 



The flies from the above puparia emerged during the period, May 12th to 18th. 



The above observations bear out our previous supposition that the usual stage 

 in which the insect winters in Canada is the puparium stage. 



Control Experiments. 

 Poisoned Bait Spray Used. 



The poisoned bait spray which has been used in our experiments in 1916 

 and 1917 is the one referred to in our Entomological Bulletin No. 12, as follows: — 



Sodium arsenite 5 grams (close to y^ oz.) 



Molasses 1 pint. 



Boiling water 1 gallon. 



The sodium arsenite was first dissolved in the boiling water and the molasses 

 then added. When the mixture had cooled it was ready for use. 



In both years we used a plot one-half acre in extent. In 1916, our work 

 was largely interfered with owing to rains which fell, in several instances soon 

 after the applications were made. Notwithstanding, however, such adverse 

 weather conditions the results from the experiment were certainly of a very 

 promising nature. In 1917, the experiment was continued on the same farm 

 and our results were indeed most satisfactory. Applications of the poisoned bait 

 were made by Mr. I. T. Barnet, who assisted in this w^ork, on June 13 (plants 

 about four inches high) ^Oth and 27th, and July 4th and 16th — five applications 

 in all. On this latter date the onions were about one foot high on the average 

 and were making such rapid growth that it was decided no further applications 

 would be advisable. The flies were readily attracted to the bait and on occasions. 

 a day or two after the mixture was applied, .dead- flies were easily found which 

 had fed upon it. 



The mixture was applied as coarse drops from a watering can with a small 

 hose. The half-acre plot was quickly gone over. Mr. Barnet began at one end 



