18 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 47 



cause considerable damage to the hawthorn, distorting leaves 

 and shoots by their removal of plant juices. The life history of 

 this aphid is probably a complicated one and is not well known. 



Control Measure 3 (end of circular) applied with force. 



European Red Mite, Panonychus ulmi (Koch). — Leaves of 

 hawthorn or crab lacking a glossy, green appearance and hav- 

 ing a somewhat blanched, or brown, dry look and a tendency to 

 curl are signs of damage produced by hundreds of tiny red mites 

 of this species feeding on both leaf surfaces. Brick red in color, 

 the adults of the European red mite are scarcely the size of pin- 

 heads. They have bristle-like hairs curving backward over their 

 robust, globular bodies. The female deposits her eggs, which 

 look like tiny cherries, in great numbers on both leaf surfaces. 

 Development of the mite occurs through a series of molts. The 

 white, discarded molt skins of a great number of young mites 

 make infestations conspicuous. Rasping of the leaf surfaces 

 and withdrawal of chlorophyll and plant juices cause serious 

 damage to the plants infested. 



Control Measure 9 (end of circular) . 



San Jose Scale, Aspidiotus perniciosus Comst., fig. 12. — 

 Probably the best known of the scale insects, San Jose scale is 

 widely distributed and is a serious pest on many trees and 

 shrubs. Heavy infestations encrust limbs and branches, causing 

 them to die. Scraping an infested branch with a thumbnail or a 

 knife squeezes the yellow juice from the saclike insects beneath 

 the gray to black, circular shells, each about one-sixteenth inch 



Fig. 12. — San Jose scale: infestation on bark of tree. A yellow saclike 

 insect is beneath each circular shell shown here. The shells are each about 

 one-sixteenth inch in diameter and gray to black in color. 



