1919 



ENTOMOLOGICAL SOCIETY 



83 



by the time the petals drop. The period of incubation varies, according to the 

 temperature, from 8 to 32 days, the average being about three weeks. The newly 

 hatched nymphs migrate to the opening buds where they feed chiefly on the 

 petioles and blossom stems. They grow rapidly and after moulting five times 

 reach the adult stage^ in about one month. This first brood is then succeeded 

 by three other broods, and the life cycle is finally completed in the fall by the 

 appearance of the winter adults — the hibernating forms. 



The Egg. 



Description: The egg (Fig. 18) is sub-oval, blunt at the base and pointed at 

 the apex. In colour it is creamy or pale yellowish with orange at the base. In 

 length it varies from .315 mm. to .340 mm. 



The egg is attached to leaf or bark by a short stalk projecting from near 

 the basal end, and at the apex there is a long hair-like filament. 



Fig. 16. — ^Showing eggs along 

 midrib of leaf. (Much enlarged.) 



Fig. 17. — First generation eggs laid on bark. 

 (Much enlarged.) 



Location of Eggs : The overwintering females deposit their eggs on the twigs, 

 fruit spurs and smaller branches, chiefly on the under surface. (Fig. 16). After 

 the buds have burst, belated females may be found laying their eggs on the young 

 leaves. 



The eggs of the summer forms are laid principally on the leaves, singly or 

 in clusters, along the midrib (Fig. 17). They also may be found on the leaf 

 petioles and shoots. 



Period of Incubation: In the case of first generation eggs, i.e., eggs laid by 

 overwintering females, the period of incubation was determined in 1917 from a 

 study of 21 batches of eggs deposited at various dates from April 14th to June 9th. 

 The average period was about 20 days, the maximum and minimum being respec- 

 tively 32 and 8 days. The average duration of the egg stage in April was 26 days, 

 in May 19 days, and in early June 11 days. (See Table No. 1). 



