INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 



79 



lence is the most serious apple pest in many of the northern counties. 

 The winged forms are distinguishable by their dusky protruding wings. 

 The fall and early winter lice are dark yellowish or brown in color. 



Fig. 61. 



-The woolly apple aphis, Eriosoma lanigera (Hausm. ), 

 on apple twig. Enlarged twice. (Original) 



Life History.— In summer, especially during the months of July 

 and August, the woolly apple aphis is exceedingly abundant upon 

 the limbs of the trees, covering large patches with their extensive 

 colonies. Towards winter it gradually disappears, only a few indi- 

 viduals remaining hidden under protecting bark or in crevices. In 

 the fall each winged viviparous female gives birth to five or six 

 males or females which mate, each female laying a large egg which 

 constitutes the over-wintering form. 



In the spring the over-wintering eggs hatch into stem-mothers, which 

 give birth to young. These mature in about ten days and continue to 

 repeat the process of bringing forth living lice until thousands appear 

 upon the trees. The succeeding broods attack both the limbs and roots 

 throughout the summer and fall. Probably some of the viviparous 

 females pass the winter on the roots in our mild climate. There are 

 probably also alternate hosts, as shown in the investigations of Dr. 

 Edith M. Patch of the Maine Agricultural Experiment Station. 51 



Nature of Work. — The large knots are produced upon the limbs 

 and roots by this aphid. These enlargements prove serious handicaps to 

 the growth of the trees, so that both old and young ones are unable to 

 grow normally or produce good crops when infested. 



Distribution. — This species occurs in practically every section 

 where apples are grown in the State. 



'Bui. No. 220, Maine Agrcl. Exp. Sta. Nov. 1913. 



