b BULLETIN 90, IT. S. DEPARTMENT OF AGRICULTURE. 
winter, sexual forms and eggs of this species are not produced, at 
least until parthenogenetic reproduction causes deterioration. 1 
In other parts of this country where the winter conditions are more 
severe the rose aphis passes the winter in the egg stage. At Wash- 
ington, D. C, on November 29, 1912, the writer found a few eggs 
of this species laid on the twigs of rosebushes. These small, oval, 
shhiing black eggs were fastened to the sides of dormant buds. 
Buckton 2 described the eggs as follows: 
The eggs are at first yellow, but subsequently they become black by reason of 
certain changes shown by Balbiani to result from fecundation. Previous to this time 
the outer coats are sufficiently thin and transparent to allow the process of segmentation 
to be observed. 
Notwithstanding the great size of the ovum the female may carry five or more. 
These, however, are not equally large, but are found to vary in bulk as they approxi- 
mate maturity and the time for expulsion. 
In California during the fall and spring, while the rose shoots are 
growing vigorously and producing much tender growth, the rose 
aphis reproduces very rapidly. During the summer, however, the 
rate of reproduction seems to be much reduced, and, owing to the 
attack of natural enemies, this insect does not greatly increase. 
In the winter the time of development is lengthened and the rate 
of reproduction is considerably less. 
During the months from October, 1909, to March 10, 1910, the 
author endeavored to ascertain the number of young produced and 
the average rate of reproduction under normal conditions. This 
was done by marking rose twigs having a single female and, after 
examining them every other day, removing all the young born at that 
time. Thus the aphides were exposed to temperature, rain, and 
all other natural conditions which might influence them. Under 
this method many females were knocked from the bushes and lost, 
but as this would occur naturally it demonstrates fairly well the 
average rate of reproduction, if not the maximum, under the condi- 
tions most favorable for the adult. These records have all been 
included in Table I. 
1 B. M. Lelong, in the Report of the State Board of Horticulture for California, for 1SS9, page 213, states 
that " Kyber, in 1815 , has had the rose aphis producing young for four years. From his carefully conducted 
experiments and from corresponding ones made bj' other naturalists a law has been educed, which we dare 
not destroy, 'that under certain circumstances, a female aphis may without coupling continue propagating 
to infinity, provided that the necessary conditions for the development of the young— food and heat— are 
not wanting.' " 
2 Buckton, G. B., Monograph of the British Aphides, vol. 1, p. 107-108, 1875. 
