30 



at the bottom of the trees than with pot-generated gas, whereas the 

 reverse was found to be the case at the top of the tree. The total 

 result for the whole tree is slightly favourable to the pot treatment 

 showing that the above amount of liquid hydrocyanic acid is insufficient, 

 to produce results equivalent to one ounce of sodium cyanide in pot- 

 generation. 



The experiments were conducted on medium-sized trees at a tem- 

 perature of from 65° to 70° F. In experiments performed under 

 similar conditions but at higher temperatures of fumigation and with 

 the use in some cases of 21 to 22 c.c. of liquid hydrocyanic acid as 

 ec^uivalent to the ounce of sodium cyanide, the mortality averaged 

 above 99 per cent. It is apparent that from 16 '56 to 21 c.c. of the 

 liquid are required to produce results similar to those secured by pot 

 generation, 18 c.c. being the average equivalent of one ounce of sodium 

 cyanide on average-sized trees at the ordinary temperatures of treat- 

 ment. A table is given of the results of experiments against 

 Chrysom'phalus aurantii on small trees, which show that the liquid 

 hydrocyanic acid is less efficient in this case. 



At low temperatures, such as 40°F., it is necessary to increase 

 the dosage of liquid hydrocyanic acid, as its superiority to pot-generated 

 gas is less marked than at higher temperatures of fumigation. 



Peterson (A.). Response of the Eggs of Aphis avenue, Fab., and 

 Aphis pom , DeG., to various Sprays, particularly concentrated 

 Lime-Sulphur and Substitutes, Season of 1918-1919. — Jl Econ. 

 Entom. Concord, N.H., xii, no. 5, October 1919, pp. 363-386. 



"With a view to determining the most efficient insecticide to be used 

 against the eggs of Aphis*avenae, F., A. pomi, DeG., and A. sorbi, 

 Kalb., experiments were carried out during the season under review 

 the results of which are almost identical with previous ones, 

 [R.A.E.,A.,Yi, 110]. 



The present observat ons were made on a larger scale and special 

 precautions were taken to avoid possible errors. In a footnote 

 (presumably by the Editor) it is stated that the species referred to as 

 A. avenae is apparently A. prunifoliae, Fitch, and as A. sorbi is 

 A. yncdifoliae, Fitch [see also R.A.E., A, vi, 47, 298 ; viii, 18, 19]. 



It was noticed that although A. avenaewas very abundant, compara- 

 tively few leaves were curled when this was the only species on the 

 tree, but if A. pomi or A.sorhi were present, even in very small numbers, 

 the leaves were badly curled and stunted. All three species were 

 present on the petioles of flowers in the pink bud and flower stage 

 and they probably injure the set of the fruit. So far as is knovNTi, 

 A. avenae does not cause small distorted fruit as does A. sorbi. The 

 latter lives on the apple plant for 3 or 4 generations and does not 

 migrate until the end of June, whereas A. potni remains throughout 

 the year on the apple ; the stem-mothers of A. avenae give rise to 

 nymphs the majority of which develop wings and migrate to other 

 plants, completely disappearing by the end of May. The damage 

 caused by A. avenae is so slight that, unless it is accompanied by 

 other species, its presence may be completely ignored. As A. pomi 

 and A. sorbi hatch 10 to 14 days after A. avenae, their presence may 

 be determined by this means; but in districts where A. pomi and A. sorbi 

 hatch too late for a dormant spray of lime-sulphur and nicotine to 



