14 MASS. EXPERniEXT STATION BULLETIN 375 



Feeding During Instars 



During the feeding period, the larvae moult four tunes and their growth 

 is divided into four instars. As shown in Table 8, at 70° and 80° F., ap- 

 proximately 3 percent of the total number of eggs were eaten during the 

 first instar, 12 percent during the second, 25 percent during the third, and 

 60 percent during the fourth. Since normal development does not take 

 place at 60° F., the records at this temperature naturally vary somewhat 

 from those at the more favorable temperatures. 



As shown in Table 4, an average mealybug egg mass contains from 250 

 to 350 eggs and it is, therefore, apparent that one mealybug egg mass sup- 

 plies enough food as eggs to feed a Cryptolaemus larva during the first two 

 instars or during the third instar. Furthermore, this indicates that unless 

 several larvae are grouped together at a cluster of mealybugs, the larva 

 will not be forced to migrate in search of food until the third instar or 

 after. 



There is a definite decrease in feeding just before each moult which may 

 last only a few hours and be scarcely noticeable in the daily feeding 

 records or may extend over two or three days. In these records the 

 moulting periods were variable but usually occurred at the following times: 

 5th to 10th day, 13th to 18th day, 23d to 29th day, and 35th to 44th day. 



Table 8. Feeding of Cryptolaemus Larvae on Eggs of the Citrus 



Mealybug at Constant Temperatures by Instars. 



Waltham. Mass.. 1937. 



*There appeared to be a fifth moult by this larva at 60° F., due to delayed development 

 at unfavorable temperature, but this was not definitely determined. 

 **Only one larva lived beyond the 1st instar. 



Percentage of Available Mealybug Eggs Eaten 



At 60° F. the Cryptolaemus larvae ate only 35 percent of the mealybug 

 eggs supplied to them during the 25 days which they lived, and this further 

 indicates the retarding efifect of low temperatures. At 70° F., about 75 

 percent of the available eggs were eaten, and there was a difference of 

 only about 6 percent between the maximum and minimum which indicates 

 favorable conditions. The greatest feeding was observed at 80°; F. where 

 82 percent of the eggs were eaten, and it is apparent that many of the 

 uneaten eggs were those supplied during the moulting periods of the 

 larvae. 



