April '11] herrick: cabbage aphis 219 



THE CABBAGE APHIS, APHIS BRASSICAE 



By Glenn W. Herrick 



Mr. J. W. Hungate, a graduate student in entomology at Cornell 

 University, made a careful study of the habits and life history of the 

 cabbage aphis during the late fall, winter, and spring of 1909 and 1910 

 under the direction of the author. Since Mr. Hungate left the work, 

 the author has carried it on repeating the observations in large part. 

 The life history of the aphis has now been followed nearly a year from 

 the stem-mothers, and experiments in the control of the pest have been 

 made during the past season. The results of these studies and experi- 

 ments are here briefly given. 



Economic Importance of This Insect 



In 1890, 1903, and 1908 this aphid was very numerous, widespread 

 and destructive in the state of New York. Moreover, our records 

 show that we received more inquiries regarding the cabbage aphis 

 during 1909 and 1910 than about any other insect pest. It was exceed- 

 ingly abundant and seriously injurious in all parts of New York State 

 during the season o*" 1909 and appeared again in 1910, but did not 

 prove nearly so injurious as last year. It not only destroys wide areas 

 of cabbages, but many fields of cabbage were either entirely abandoned 

 or plowed up early in the season of 1909 from a feeling of utter inability 

 to check the pest. Some fields were plowed up in 1910 rather too 

 early, for in most cases the parasites and predaceous enemies soon 

 became abundant enough to hold the aphis in check. 



Seasonal History of the Aphis 



The oviparous females appear in the fall, are fertilized by the males, 

 and deposit their eggs in large numbers on the leaves of the cabbage. 

 The eggs were deposited freely during the month of October and first 

 days of November. The first eggs were noted on October 10, 1909. 

 No doubt some were deposited before this date. There seems to be 

 no question but that the eggs are deposited on cabbages in great 

 numbers and that a great majority of the eggs are fertile and hatch in 

 the spring. Eggs were found on cabbage, rape, turnip, brussels sprouts 

 and kohl-rabi, but in small numbers except on the cabbage. They were 

 deposited in greatest numbers on the undersides of the cabbage leaves 

 and were usually placed in depressions and crevices of tlie leaves. 

 The egg, when first laid, is of a pale greenish yellow color, but usually 

 soon turns dark and. finally becomes almost black. 



