66 



THE REPOET OF THE 



No. 36 



TABLE No. 2— Sexupar^— M. CERASI. 



The Male. 



Early in October winged males* appear on the secondary host and fly back 

 to the cherry where they mate with the oviparous females. No males are pro- 

 duced on cherry. This means that, in spite of the pronounced tendency of the 

 black cherry aphis to live a monophagous life on cherry, the completion of its 

 life cycle is still dependent on the existence of a secondary host. 



Description. Antennae, head, thorax, cornicles and external genitals black. 

 Abdomen reddish brown with dark transverse bars, and three black lateral spots. 

 Length 1.53 mm. to 1.62 mm, 



Nymphal Life. 



The average duration of nymphal life of 29 individuals was 35 days, the 

 maximum and minimum being respectively 25 and 4-i days. 



The Ovipaha, 



This form may be found on the leaves, twigs and branches up to the time 

 all the aphids are killed by frost. 



Description. The general colour of the ovipara is dark brown. The abdo- 

 men may be tinged with green. In size, it is about 1.8 mm. x .8 mm. 



Breeding Experiments. 



In our experiments with 13 individuals the following data were obtained: — 



Length of Nymphal Life : Maximum 33 days, minimum 21 days, average 

 27.4 days. 



Age when egg-laying commenced: Maximum 53 days, minimum 26 days, 

 average 40.2 days. 



Reproductive period: Maximum 22 days, minimum 1 day, average 10.2 days. 



Fecundity per female: Maximum 8 eggs, minimum 1 egg, average 4.2 eggs. 



Longevity: Maximum 71 days, minimum 52 days, average 61.6 days. 



Number of Gexerations. 



According to our experiments there are from six to fourteen generations of 

 this insect per year in the Niagara district. 



*Males developed on Lepidium from October 6th to November 17th. 



