INSECT PESTS OF OHIO SHADE AND FOREST TREES 281 



expels them covered with a thin, sack-hke membrane which is soon 

 broken open, allowing the insect to emerge. 



Life history and habits. — The winter is passed in a partly- 

 grown condition beneath the shelter of the round scale cover, which 

 at that time is coal black. With the advent of spring, growth 

 continues and the males mature and emerge from beneath their 

 scale coverings. They seek the females, mate and perish. By late 

 June the females have matured and the crawling young insects 

 begin to appear. Upon finding a suitable place, they settle down 

 upon the host, insert their hairlike, needle-sharp beaks into its 

 tissue and begin to imbibe the sap. White waxy hairs now spring 

 up from pores in the insect's back, which mat it over, forming a 

 pure white covering, and after several days this turns black. In 

 about 2 weeks the insect molts, losing its legs and antennae and the 

 females their eyes. With continued growth and successive molts 

 the scale is enlarged. The males mature in from 3 to 5 weeks and 

 mate with the females, but the latter do not reach maturity until 

 they are from 4 to 7 weeks old. 



Each female may produce several hundred young but perhaps 

 does not average more than 150 to 200. This period of production 

 extends over several weeks. Thus the first-born themselves may 

 be producing young before the last of their sisters are born, and 

 this accounts for the fact that the insect in all stages of development 

 may be seen during the summer. 



There are several broods per year. 



Nature of work. — The hundreds of thousands of sap-sucking 

 scale insects of a badly-infested plant rob it of its juices and liter- 

 ally dry it up, ultimately resulting in death. With most infested 

 plants it will be noted upon cutting into the bark or when examining 

 fruit or foliage that the lighter-colored parts usually are stained 

 red. This and other indications have led to the belief that in addi- 

 tion to the mechanical injury resulting from the loss of sap, the 

 insect may exert a toxic effect upon the host. The final type of 

 injury, one which has little bearing upon the subject in its present 

 consideration, is the spotting or discoloration of fruit and foliage 

 due to the attacks of this species. 



Food plants. — Dr. W. E. Britton (39), in his second annual 

 report, published a list composed of 138 species of plants upon which 

 the San Jose scale is known to subsist. This list was later repub- 

 lished by Doctor Felt (28). By referring to either of these publi- 

 cations the reader will see that this species may be considered a 

 general feeder, although on the other hand some of our best trees 

 are not subject to attack by it. 



