14 BuLi.t;TiN ;^2H 



Destroying the Af^his in the Pall 



In the fall the return of the aphis usually covers a considerable 

 period. In the late fall shining black eggs, immature yellowish 

 eggs and adult aphids are found on the same twig. Anything 

 short of several sprayings would seem to be doomed to failure as 

 a method of control. 



Destroying the Aphis in the Egg Stage 



Throughout the winter and earl}' spring the eggs remain on 

 the tree, open to attack, and this would seem to be the logical 

 time to compass their destruction. Alaiiy efforts have Ijeen made 

 to find a substance which Wijuld destroy the aphis egg, not harm 

 the tree, and sell for a price that would not prohibit its use. It 

 can truthfully be said that up to the present time no such sulv 

 stance has been given to the pu1)lic. 



During the winter and spring of 1917, Dr. Peterson made a 

 preliminary study of the egg and of the effects of certain 

 chemicals upon it. He found that the egg envelope exhibits at 

 least two layers — an outer semi-transiiarent brittle envelope ( glu- 

 tinous wdien the egg is first deposited ) and an inner pigmented 

 elastic meml)rane. A third layer may l)e seen as the nymph 

 hatches, but this is probal)ly the first-cast skin of the nymph. 

 The outer layer appears to exercise a protective function, 

 resisting strains and stresses and retarding evaporation of 

 the body fluids. The fact that this transparent layer encloses 

 the pigmented layer leads one to suspect that, like the jelly on a 

 frog's egg. it may keep the egg warm hv transnntting the sun's 

 rays and retaining the heat into whicli thev are transformed b\- 

 the pigment. 



Sometime l>efore hatching, the ])eriod ranging from two to 

 thirty days, the outer layer splits along the median line, exposing 

 the pigmented layer, and the egg is thereafter very sensitive to 

 weather (dry air particularly) and insecticides. 



In the course of his experiments. Dr. Peterson found that the 

 eggs were strongly affected Ijv carljolic acid and l)v winter- 

 strength lime-sulfur. He found that the carbolic acid appeared 

 to soften the outer brittle layer in such a fashion that the egg 

 soon shriveled, while the lime-sulfur appeared to harden it and 

 to prevent hatching. 



Table T, taken from Dr. Peterson's work, will serve to show 

 the effect of our common sprays upon the eggs and to indicate 

 some sul)stances worthy of further trial. The table is the sum- 

 mary of a large series of experiments. The percentage killed is 



