THE CANADIAN ENTOMOLOGIST 271 



Fig. 10 is primarily a data sheet. Here the letters of the 

 alphabet are used to designate r'the several increments of 100 

 females collected. The groups of figures extending diagonally 

 across the plate represents milligrams of eggs deposited on suc- 

 cessive nights from February 27th until March 24th, inclusive. 

 The first four figures of each horizontal row indicate the deposits 

 of a single increment during the first four nights in the insectary; 

 the fifth, all after the fourth night until the entire increment of 

 100 females was dead. The last vertical column represents, in 

 days, the length of time each increment was kept; the column 

 next to this the total number of milligrams of eggs deposited by 

 each increment. A grand total of the eggs deposited by the 

 2,500 females appears below as well as the average number of 

 days the insects were kept before all were dead. 



The number of eggs to the milligram was computed by counts 

 made of the eggs deposited by increments O and R on the nights 

 of March 14th and 18th, respectively, these masses being ex- 

 ceptionally free from foreign particles. The count on the former, 

 weighing 330 milligrams was 3,851 or 11.67 eggs to the milligram; 

 that on the latter, weighing 250 milligrams, was 2,930 or 11.72 

 eggs to the milligram. These results were considered close enough 

 to warrant the adoption of 11.7 to be used as a multiplier in chang- 

 ing milligrams to number of eggs. 



Table III shows the number of eggs considered in computing 

 the incubation period for different parts of the season, together 

 with the total number of eggs upon which was based the de- 

 termination of the average number of days spent in the egg stage. 



Table IV gives the datg. upon which the calculation of the 

 average percentage of fertility of the eggs depends. In each case 

 the letter in the first vertical column specifies the particular in- 

 crement whose total number of eggs deposited during each suc- 

 cessive night is designated and totalled; whose sterile eggs deposited 

 during each successive night is recorded and totalled; and the 

 computed percentage of sterile eggs for each night's deposit ap- 

 pears with its average. At the bottom of the table appear grand 

 totals which show an almost identical percentage of sterility in 

 the first two nights' deposits with an increase thereafter approximat- 

 ing a geometrical ratio. 



