CONTROL OF MEALYBUGS 



13 



Rate of Feeding on Mealybug Eggs 



Naturalh', the larvae eat more rapidly as they grow larger, and in 1935 

 during the first 50 days at 70° and 80° F. this increase in feeding was quite 

 regular. When the activity was grouped according to ten-day periods, 

 the maximum feeding occurred in the 41-50 day interval when the larvae 

 ate 30.9 eggs per day at 70° F. and 47.47 eggs per day at 80° F. Some 

 larvae ate 59 eggs in one day during this time, which was the greatest 

 daily feeding recorded in these experiments. Most of the larvae, especially 

 at 80° F., began to pupate within a few days after the 50-day period and 

 after that point the rate of feeding decreased as it does before each moult. 

 At 70° F. the larvae lived about 62 days, and the decreased feeding after 

 the 50-day period was not so evident. Since no larvae lived more than 

 38 days at 60° F. and none completed larval development, the rate of 

 feeding is not comparable with that at the higher temperatures. It does 

 show, however, that the cooler temperature greatly retarded rate of feed- 

 ing at all times. 



The rate of feeding on mealybug eggs by larvae of Cryptolacmus montrou- 

 zieri at 60°, 70° and 80° F. is shown graphically in Figure 2. 



LENGTH OF LIFE OF 



iRVAE IN DAYS 



Figure. 2. Rate of Feeding of Cryptolaemus Larvae at Constant Tennperatur 

 Waltham, Mass., 1935. 



Determined from the average number of mealybug eggs eaten per beetle per day by 

 Cryptolaemus larvae when supplied with a known number of eggs per day. 



At 60° F. At 70° F. At 80° F. 



Average number of larvae feeding per day 6.02 5. 5.4 



Maximum number of eggs eaten by a larva in 1 day 16 55 59 



