1918 ENTOMOLOGICAL SOCIETY. 65 



Reproductive period: Maximum 26 days, minimum 2 days, average 11.6. 



Fecundity: The average reproductive capacity of 18 individuals was 16.7 

 voung per insect, the maximum and minimum being respectively 37 young and 

 4 young. 



Daily production of young : Maximum 8, minimum 1, average 1.7. 



Total length of life : Maximum 56 days, minimum 4 days, average 15.4 days. 



Secondary Apterous Vivipara. 



The progeny of the cherry to Lepidium migrants develop into wingless vFvi- 

 para and are followed by brood after brood of their kind until fall at which 

 time return migrants and males are produced, concerning which more will be 

 said later. For want of a better name, the wingless forms on Lepidium are 

 referred to in this paper as secondary apterous vivipara?. 



Description. This form is much smaller and is lighter in colour than its 

 fellow on cherry. It is dull brown in colour and is about 1.26 mm. x. .68 mm. 

 in si^e. _ 



Breeding Experiments. 



In experiments with 37 apterous forms the following data were obtained. 



Length of Nymphal Life : Maximum 19 days, minimum 6 days, average 

 9.8 days. 



Age when reproduction commenced: Maximum 19 days, minimum 6 days, 

 average 10.2 days. 



Reproductive period: Maximum 44 days, minimum 9 days, average 24.5 days. 



Reproductive capacity per female: Maximum 83 young, minimum 19 young, 

 average 44 young. 



Daily production of young per female : Maximum 7 young, minimium 1 

 young, average 1.8 young. 



Total length of life: Maximum 75 days, minimum 17 days, average 40.8 

 days. 



The Alate Sexupara. 



In early autumn migrant aphids* are produced on Lepidium and return 

 to the cherry where they deposit the egg-laying females. At the same time the 

 monophagous lines on cherry give rise to large numbers of winged forms f which 

 also give birth to egg-laying females. In other words the sexupara — the mother 

 of the sexual female — is produced on botli the secondary and primary hosts. 



Description. This form is very similar in appearance to the summer 

 migrant. 



Breeding Experiments. 



The data obtained from the sexupara^ bred on cherry (primary host) and on 

 Lepidium (secondary host) are presented herewith in tabular form. 



*Return migrants were found on Lepidium from Sept. 17th to October 29th. 

 ^Sexuparw were produced on cherry from Sept. &th to the close of the season. 

 5 E.S. 



