330 



REPORT OP STATE BOARD OF HORTICULTURE. 



an egg the female would move back to a leaf or a stock and resume feeding-. 

 It is probable, the eggs being so large in proportion to the size of the insect, 

 that only a few are developed, and that an interval of a day, or perhaps 

 more, may intervene between deposits. 



It is certain that after the beginning of September development is much 

 less rapid than in early summer, the seventh series of breeders ranging- 

 from September 12 to November 1, though after October 1 in constantly 

 decreasing numbers. 



Kig. 32 — Sexes of the apple plant lou.se : Male, to the left, with antenna, honey tube, and 

 terminal segment yet further enlarged; female, to the right, with antennal pitting!* 

 and posterior tibia more highly magnilled. 



This life-history covers the period from the egg deposited in the fall of 

 1898 to the egg deposited in the fall of 1899. The number of forms proved 

 unexpectedly large and there may be more than I discovered. It will be 

 necessary, before we can say that the life-history of this insect is entirely 

 known, that each series be separately colonized and its descendents studied, 

 free from admixture of other forms. 



SUMMARY. 



The apple plant louse hatches from the egg as soon as the buds begin to 

 develop in early spring. In about fifteen days a stem-mother becomes 

 developed and begins to reproduce. Nine or ten days thereafter a second 

 series matures, of which about three-fourths become winged. A third 

 series matures about two weeks later, and of these less than one-half are 

 winged. Thereafter no more winged forms are produced, but seven series of 

 parthenogenetic females are in all produced, each series having peculiarities 

 of its own. The winged forms leave the tree upon which they develop, liy 

 to others and so spread the species in all directions in early summer. Sexed 

 individuals are produced in October, and egg-laying begins about the tenth. 

 It continues until late in November or, in southern counties, until the eai-ly 

 portion of December, the eggs being black, shining, and laid around the 

 buds, in the crotches, or in crevices generally on the trunk and branches. 



NATURAL ENEMIES. 



In the course of the season I found among these aphids two species of 

 Coccinellids or "lady-birds," three species of Syrphids or flower flies, one 



