THE ROSE APHIS. 9 
Of four other aphides, born on October 10, two became adult and 
gave birth to young on October 22, or in 11 days, while another 
required 12 days, and the fourth 13 days. 
Another aphis was born on October 19 and emerged as a winged 
female on November 3, reaching maturity in 15 days. This insect 
lived as an adult for 17 days and gave birth to living young for 14 days. 
During this time she gave birth to 87 young, or an average of 6^ per 
day. During this time the average mean temperature was 67° F. 
LIFE CYCLE IN CALIFORNIA. 
During the whiter months of 1909-10 the life cycle was observed in 
California in a number of cases. Aphides born on the 18th of Novem- 
ber became adult wingless females and began to reproduce young in 
from 15 to 18 days, and in two cases the offspring of these same insects 
became mature and began to reproduce in from 18 days for wingless 
females to 21 days for winged females. Aphides born November 26 
emerged from nymphal skins as winged adults in from 23 to 25 days. 
Thus the wingless forms developed in all cases from 7 to 8 days sooner 
than winged forms. 
This was the maximum life cycle, and during the rest of the year 
the growth must have been much faster, but observations were not 
made owing to press of other matters-. 
GENERATIONS. 
Taking 25 days as a maximum, this would allow more than 12 
generations annually, but with the shorter life cycle required during 
the warmer part of the year this number must be exceeded by at least 
7 or 8 generations. In greenhouses there are probably 25 to 30 
generations hi a -vear. 
LONGEVITY. 
During the whiter these bisects are long lived for such delicate 
creatures. One lived under the direct observation of the writer for 
40 days and another for 33 days. Probably this is longer than for 
the same insect the rest of the year. 
NATURAL CONTROL. 
RAINS. 
Iii southern California the rainy season extends from about October 
1 to May or June. Usually before the rains set in the weather becomes 
cooler, but the rams are not as a rule hard and dashing, as are those 
so fatal to aphides in the East, and this apparently explains their 
slight effects as observed on the rose aphis. Undoubtedly some are 
washed away and destroyed by ram, but not to the extent occurring 
in the East, although reproduction seems to be greatly checked during 
a rainstorm. In the East this insect is many times nearly extermi- 
nated bv a hard, dashing rain. 
