PROCEEDINGS, 1916. 



55 



TOTAL NUMBER OF GENERATIONS. 



Fig 1. Generation of Aphis malifoliae Fitch, 1916. 



In 1915 we secured a maximum of nine generations with this species, but in 1916 

 a maximum of ten was produced. As will be seen in the figure there is a great overlap- 

 ping of generations and the last three are cut short by the arrival of cold weather. 



THE TOXIC VALUE OF SOME COMMON POISONS ALONE 



AND IN COMBINATION WITH FUNGICIDES, ON A FEW 



SPECIES OF BITING INSECTS. 



By G. E. Sanders, 

 Dominion Entomological Laboratory, Annapolis Royal, N. S. 



and W. H. Brittain, 



Provincial Entomological Laboratory, Truro, M- S. 



DURING the season of 1915 a number of tests were made with various poisons, 

 both alone and in combination with fungicides. These preliminary tests brought 

 to light the interesting fact that arsenic compounds appeared to have their ef- 

 fiency reduced when used with lime sulphur, and this reduction in toxic value was still 

 more marked when Bordeaux mixture was used. On the other hand, when added to 

 sodium sulphide (soluble sulphur) the killing power of the different arsenicals seemed to 

 be noticeably increased. 



The result of one of the foregoing experiments seems worthy of record. It has 

 always seemed probable that the browntail moth (Euproctis chrysorrhoea) was, to a 

 large extent, controlled by the last summer sprays, applied during late June and early 

 July.although over a month elapses between the application of the spray and the hatch- 

 ing of the larvae. As definite experimental data on this point was lacking, a number of 

 tests were arranged. On July 7th the various poisons alone and in combination with 

 fungicides were applied to a number of trees at Round Hill, Annapolis Co. Later, 

 three browntail moth egg-masses were placed on each of these trees, attached to leaves 

 showing evidence of an average quantity of the spraying material. On October 10th, 

 1915, the young browntail moth larvae emerged and commenced feeding. In Novem- 

 ber the nests were gathered, the number obtained from each combination being 

 shown in Table No. 1. 



