56 MASS. EXPEKIMENT STATION BULLETIN 189. 



shape into a more flattened one. From 5 to 50 eggs are thus deposited in 

 a flat egg-mass, each egg overlapping the adjoining one in the manner of 

 shingles. The female rarely changes her position during the oviposition 

 of an egg-mass, as the flexibility of the abdomen allows quite a radius of 

 action. 



Distribution of Egg Masses. 



During its period of fertility the female deposits a varying number of 

 egg-masses, each mass being composed of from 5 to about 50 eggs. These 

 are generally placed on the under sides of the leaves of several different 

 plants, but in some instances all of the eggs may be deposited on the 

 same plant. When selecting plants for egg deposition the female appar- 

 ently prefers certain plants to the exclusion of others belonging to the 

 same species. 



In life-history cages the daily rate of oviposition varied with different 

 females and according to the temperature conditions. In some instances 

 a single female deposited several egg-masses in twenty-four hours, while 

 in other instances a period of several days elapsed between the deposition 

 of successive egg-masses. 



Total Number of Eggs deposited by Each Female. 

 First Generation. 

 In Ufe-history cages 13 female moths of the first generation deposited 

 an average of 545 eggs each. The maximum number of eggs deposited 

 by a single female was 903, and the minimum, 132 (see Table V). 



Second Generation. 

 In life-history cages 15 female moths of the second generation deposited 

 an average of 337 eggs each. The maximum number of eggs deposited 

 by a single female was 727, and the minimum, 107 (see Table XI). 



Duration of Fertility. 

 The duration of fertility is here considered to be the period between 

 the first and last deposition of eggs. 



First Generation. 

 The duration of fertility of 13 female moths of the first generation that 

 were confined in Ufe-history cages during July and August, 1918, aver- 

 aged fifteen days, with a maximum of twenty-four days and a minimum 

 of six days (see Table V). 



Second Generation. 

 The duration of fertility of 15 female moths of the second generation 

 that were confined in life-history cages during May and June, 1918, 

 averaged 13.66 days, with a maximum of twenty-one days and a minimum 

 of six days (see Table XI). 



