INJURIES BY ROUNDHEADED BORERS. 



355 



borer, so that there is scarcely any season of the year when trees may 

 be cut and left with bark on, without danger of being damaged by 

 this borer. 



THE OAK PRUNEK. 



(Elaphidion viUosum Fab.) 



In the oak primer we have a species which attacks only twigs or 

 small branches on living and injured trees, causing them to break and 

 fall to the ground. If occurring in large numbers it is of consider- 

 able economic importance, in retarding 

 the growth of twigs and branches. Be- 

 sides oak. this species attacks sassafras, 

 black walnut, hackberry, sweet gum, hick- 

 ory, and maple. Its range extends from 

 Pennsylvania to South Carolina, and as 

 far west as New Mexico. 



The larva (fig. 28,- a) is a very slender 

 white grub about one-half inch in length. 

 The adult is a slender, shining, brown 

 beetle (fig. 28, &), 11 to 16 mm. in length, 

 rather sparsely clothed with gray pubes- 

 cence, each elytron terminating in two 

 spines of about equal length. Adults fly 

 in March, April, May, and June, during 

 which time oviposition takes place upon 

 the twigs or branches. 



The young larva, after hatching from 

 the egg, first mines in the inner bark, 

 then enters the wood and girdles the 

 twig or branch by boring around it sev- 

 eral times in the same place (fig. 28), 

 leaving the bark and usually some of the 

 wood intact. The larva then mines in 



the center of the twig beyond the girdle. The twig is usually 

 broken off at the girdle by the wind and falls to the ground, carrying 

 the larva with it. Pupation takes place in the center of the twig. 

 There is apparently one generation a year, the adult usually emerging 

 in March, April, May, or June of the year following that in which 

 the egg is laid. 



When this species occurs in large enough numbers to be injurious, 

 the fallen twigs and recently killed twigs still on the trees should be 

 gathered and burned in the fall in order to destroy the larvae and 

 pupse in them. 



FIG. 28 Work of the oak 

 primer (Elaphidion rillosum). 

 Oak branch which has hcen 

 pruned, showing larval mines. 

 a, Larva ; 6, adult. Insects 

 natural size. (Original.) 



