71 
University of Illinois, made a similar series of studies. He began with 
the first hibernating females that he conld find, and traced their 
progeny. One of the females found April 8 brought forth the first 
young aphid April 17, and this acquired wings April 29. In the field I 
have seen winged individuals at all times up to November 10. 
Five apterous viviparous females studied by Snider bore, respect- 
ively, before the end of June, 104, 108, 110, 124, and 147 young. The 
last number is unusually large even for an aphid. 
Males and oviparous females were not found until October (with 
one exception — a female born September 22) ; and males were taken in 
the field October 10, 17, 20, and November 3. Copulation was observed 
in the field October 20 and November 3 ; in the last instance oviposi- 
tion began twenty-five minutes after copulation ceased. Six females 
began to oviposit, respectively, October 18, 20, 21, 31, and November 
3 and 4. One female in coitu October 20 laid eggs October 26 (2 
eggs), 29 (1), 31 (2), November 3 (1), 4 (1), 5 (1), 6 (2), 18 (2), 
and no more up to December 2, when the observations ended. A fe- 
male born September 22 laid an unfertilized ^gg October 18. A female 
taken in the field October 11, 1904, laid eggs October 21, which hatched 
March 23, 1905. The eggs have escaped the notice of previous ob- 
servers. Here, the eggs are common. 
Habits. — When these aphids are as yet few, they select the young- 
est leaves and stems of the plant, especially the under sides of the 
leaves ; but as they increase, they spread over the plant, and may 
crowd together so closely that large numbers fall to the ground for 
want of standing room. 
The rapid increase in the number of individuals is not due to any 
extraordinary prolificacy, but results from the rapid growth and conse- 
quent early maturity of each aphid and from the fact that almost every 
individual is a female. 
While the aphid is growing, the moults occur at short but variable 
intervals, as appears in the following table made from R. L. Webster's 
notes. 
M. pisi 
No. of 
First 
Second 
Third 
Fourth 
First 
genera- 
tions 
Born 
moult 
moult 
moult 
moult 
young 
1 
March 23 
March 28 
March 31 
April 2 
April 4 
April 5 
1 
March 23 
March 25 
March 31 
April 4 
April 9 
2 
April 5 
April 9 
April 12 
April IS 
April 21 
April 2S 
2 
April 5 
April 10 
April 13 
April 18 
April 21 
April 26 
3 
April 26 
April 29 
May 1 
May 3 
May S 
May 8 
4 
May 8 
May 12 
May IS 
May 20 
5 
May 20 
May 22 
May 23 
May 2S 
May 28 
May 31 
6 
June 1 
June 3 
June 5 
June 7 
June 9 
June 10 
7 
June 10 
June 12 
June 13 
June IS 
June 17 
June 19 
9 
Julyl 
July 3 
July 4 
July 6 
July 7 
July 10 
9 
July 1 
July 3 
Julys 
July 6 
July 10 
July 11 
