October, '19] PETERSON: APHID EGGS 379 



and fish-oil soap (1 gm.-200 cc, 1 gm.-lOO cc. and 1 gm.-50 cc.) and 

 given a thorough tryout. A series of interesting results were obtained, 

 but none of these gave a satisfactory control. In most instances 

 linseed oil at a given strength was somewhat more efficient in killing 

 eggs than cotton-seed oil. The greatest strength used gave the high- 

 est percentage of kill. Where Unseed oil (Expt. 41, Table I; Expt. 

 24-p, Table II) was used at the rate of 8 cc.-92 cc. of soap solution 

 (laundry soap, 1 gm.-lOO cc.) it killed 94 per cent of the eggs of 

 A . aven(£ and 91 per cent of A . pomd when applied on March 21. Where 

 appHcations were made on March 10 or previous to this the greatest 

 percentage of kill was 64 per cent or less. Where cotton-seed oil was 

 used at the rate of 8 cc. to 92 cc. of soap solution (laundry soap Igm.- 

 100 cc.) it killed 92 per cent of the eggs of A. avenoe and 90 per cent of 

 the eggs of A. ponii when applied on March 21. Where applications 

 were made on March 10 or before the percentage of kill was 54 per 

 cent or less. Crude carbolic acid at the rate of 1 gm. to 100 cc. of 

 spray was added to linseed and cotton-seed oil sprays and in the major- 

 ity of cases there was a slight reduction in the percentage of hatch 

 over the same strength of oil emulsion alone. Fish-oil soap at various 

 strengths was used to emulsify the linseed and cotton-seed oils. Where 

 fish-oil soap was used at the rate of 1 gm.-50 cc. with a given strength 

 of oil the greatest reduction usually occurred. More than likely one 

 could kill 100 per cent of the eggs by using a strong fish-oil soap and 

 at least 8 cc. to 92 cc. of linseed or cotton-seed oil and applying the 

 same near the hatching period. The principal objection to such a 

 combination would be its high cost. 



Conclusions 



The following statements concerning the structure, behavior and 

 response of the eggs of A. avenoe and A. pomi (and probably A. sorhi) 

 to environmental factors and various sprays are based on three years 

 of study. 



The eggs are covered with two distinct layers, an outer semi-trans- 

 parent hardened shell and an inner pigmented (black) soft membrane. 

 The outer shell is much more impervious to water than the inner black 

 membrane (chorion). The outer shell splits (usually) along the dorso- 

 mesal line a short time (in some cases over 30 days) before the inner 

 pigmented membrane is severed by the nymph. Evaporating factoi-s 

 apparently influence the rapidity of the splitting of the outer layer. 

 Low evaporation seems to delay the splitting, wliile high evaporation 

 probably has the opposite cfTect. Evaporating factors also influence 

 the percentage of hatch, particularly at the time when the eggs are 

 splitting their outer shells. Incubator and other experiments wiiore 



