498 Report of the Department of Entomology of the 



to seasonal conditions, but usually during April. The aphids that 

 hatch from the eggs are all females, and when fully developed 

 they give birth to living young aphids which become asexual fe- 

 males. These mature in ten to fourteen days and in turn give 

 birth to many young. In seasons favorable to the insect the num- 

 bers of the lice increase rapidly, and in a short period of time the 

 leaves of the plants become thickly covered by the greyish-green 

 creatures. At varying periods winged females make their appear- 

 ance, which seek other plants, and thus distribute the species 

 through the entire field. In the autumn the sexual forms develop, 

 which deposit eggs, thus completing the life cycle of the pest. 



The aphis is a sap-sucking insect and subsists on the juices of 

 the cabbage. The effects of the feeding of large numbers of this 

 species are either to dwarf or to kill the plants, which result in 

 the reduction of the weight and numbers of marketable heads. 



importance of the aphis to cabbage-growing in recent years. 



During the past decade severe outbreaks by this pest have been 

 of frequent repetition. Overwhelming numbers of the aphids 

 appeared in 1903, 1908, 1909, 1910 and again during 1913. 

 During these years there was, in certain sections of New York, 

 a great diminution in crop production, due in large part to shrink- 

 age in yields on account of the attacks by these insects and in part 

 to plowing under the fields of cabbage to avoid taking further 

 chances with the lice. 



The outbreak of 1913 was not so severe as some others in 

 previous years, but the injury by the aphis, coupled with the 

 prolonged dry weather, was sufficient to destroy many plantings of 

 cabbage. The lice appeared in great numbers in June before the 

 young plants were well established, and there was no cessation in 

 the multiplication of the insects in most cabbage fields till early 

 September. The rainfall during this period is recorded as the 

 smallest in many years, and because of the slight precipitation 

 the plants grew slowly and proved very susceptible to injuries by 

 the lice. The abstraction of sap by myriads of the insects and 

 the deficiency in soil moisture proved, in most fields, a severe 

 drain on the vitality of cabbage. Many of them died, while the 



