334 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



black. The young when first hatched are oval, shining, bright 

 yellow in color, and lack the mealy coat. The winged viviparous 

 female is yellowish-green, with the eyes, neck and thoracic lobes 

 black, and the antennae and nectaries dark brown. The legs are 

 dusky brown and hairy; the tail is dark green or brown and also 

 hairy; the wings are rather short, with stout coarse veins and dark 

 stigma." (Riley). 



Life History. Though the cabbage-aphis is an old European 

 species and was observed in this country as early as the latter part 

 of the eighteenth century, its life history has only recently been 

 carefully worked out by Professor G. W. Herrick and Mr. J. W. 

 Hungate of Cornell University (I.e.), from whose account the fol- 

 lowing is taken: 



The oviparous females appear in the fall and are fertilized by 



the males, and deposit 

 their eggs in large num- 

 bers on the leaves of the 

 cabbage, during October 

 and the first days of 

 November, in central 

 New York. The eggs 

 _ . are laid on rape, turnip, 



brussels sprouts and 

 FIG. 282. The cabbage-aphis (Aphis brassicce , , , , . , 

 Linn.): a, winged form; b, wingless viviparous konl-rabl but are most 

 female greatly enlarged. (After Curtis.) abundant on cabbage, 



particularly in the crevices and depressions of the under surfaces of 

 the leaves. On leaves taken at random from a badly infested patch, 

 from 177 to 293 eggs were found on a leaf. Two to three eggs are 

 laid by each oviparous female. When first laid the eggs are a 

 yellowish-green, but soon turn a shining black. From eggs taken 

 at random and left under normal outdoor conditions, 76 per cent 

 hatched the next spring, while all eggs hatched which were laid by 

 females known to have been fertilized. Eggs hatched about 

 April 1, 1910, in central New York, the season being an early one. 

 From the stem mothers which hatched from these eggs, twenty- 

 one generations of wingless females were reared up to December 3, 

 1910, the average length of a generation being about twelve days. 

 During the summer generations of winged females are produced, 

 especially on crowded plants, and these serve to spread the pest to 



