October, '19] PETERSON: APHID EGGS 371 



("Soluble sulphur"), each by itself and each in combination with 

 nicotine (Black Leaf 40, 1-500) ; to try out various other sprays and 

 combinations and also to make a preUminary determination of the 

 value of spreaders for any contact insecticide which might be used to 

 kill aphid eggs. 



The results of the majority of the spraying experiments for 1918- 

 1919, with the eggs of A. avenm and A. pomi, may be found in Tables 

 I and II respectively. The two tables show for every spray the serial 

 number, the letter representing the spray on the charts (if plotted) 

 and the dates of application. The numbers to the right of each spray 

 are the percentages of hatch of 200 to 500 eggs sprayed on the dates 

 indicated at the top of each column. The spray solutions were made 

 up in liter quantities or fractions thereof (100 cc). A solution read- 

 ing as follows: Unseed oil 8 cc.-92 cc. plus laundry soap 1 gm.-lOO cc. 

 plus crude carbolic acid 1 cc.-99 cc. means that in 100 cc. of the spray 

 mixture there is 8 cc. of linseed oil, 1 gm. of soap and 1 cc. of crude 

 carbolic acid. The same thing is true with all other sprays represented 

 in the tables. 



The most important series of experiments have been plotted in 

 Charts I-V. Each spray has been given a definite letter which is 

 the same for all the charts. The key on page 381 or the letters in the 

 first column of Tables I and II show what each letter stands for. The 

 charts show on the top line the date of application, while the columns 

 of figures to the left and right indicate the percentage of hatch and 

 the percentage of kill, respectively. The point of intersection of the 

 plotted lines with the perpendicular date lines (date of application) 

 indicates the percentage of hatch if one examines the column of figures 

 to the left and the percentage of dead eggs if one examines the column 

 of figures to the right. The percentage figures at the bottom of the 

 chart show the approximate percentage of eggs with a split outer shell 

 on the respective dates when the applications were made. 



The majority of plotted experiments show a gradual and regular 

 increase in effectiveness from the first applications made in December, 

 January and February to the last made on March 21, 1919. In a 

 few series of experiments and in the checks as well there is some irregu- 

 larity. This irregularity may be due to the fact that occasionally 

 one may work with a few abnormal eggs and still not be aware of it 

 at the time when the spray is applied. The use of a large number of 

 eggs in each experiment and the fact that collections were made from 

 various trees in the same orchard largely ehnunates the pos.sibility of 

 serious exjierimental error. In Charts II and III it will be noted that 

 on March 21 some of the experiments show a shght increase in the 

 percentage of hatch where applications were made on this date. This 



