4 INSECT DAMAGE IN TH^ NATIONAL PARKS. 



Jeffrey pine beetle, and the red turpentine beetle. All but the Jeffrey 

 pine beetle of the Sierras are common to the northern Kocky Moun- 

 tains and the Pacific Slope. Those common to the central and south- 

 ern Kocky Mountains are the Black Hills beetle, the Engelmann 

 spruce beetle, the Douglas fir beetle, and the red turpentine beetle. 

 There are three other species common to the southern Rocky Mount- 

 ains and northern Mexico ^Yhich are of less importance in causing 

 the death of trees. 



These insects are small, stout, black to reddish-brown beetles, rang- 

 ing in length from about 2 mm. to 9 mm., or 0.08 to 0.3G of an inch. 

 They fly in the period from April to October and attack the main 

 trunks of the living healthy trees by boring into the bark and ex- 

 cavating long winding or nearly straight egg galleries between 

 the bark and wood. In this manner they completely girdle and thus 

 cause the death of their victims. As soon as the bark begins to die the 

 eggs deposited by the beetles hatch and the young grubs, or larval 

 forms, complete the destruction of the inner bark. All of the broods 

 develop into the adult stage within a j^ear and emerge from the 

 bark to fly in search of neAv victims. Each species has its peculiar 

 habits in the choice of host trees, methods of attack, and period of 

 development. 



THE MOUNTAIN PINE BEETLE. 



The mountain pine beetle attacks the mountain or silver pine, sugar 

 pine, western yellow pine, lodgepole pine, and evidently all other 

 pines of the northern Rock}' Mountains and the Pacific slope. The 

 adult beetles fly in the period from July to October, inclusive. When 

 abundant they concentrate their attack on clumps and patches of 

 trees. Their long, nearly straight egg galleries and radiating larval 

 mines soon kill the bark on the main trunks, but the foliage of the 

 infested trees remains green and apparently healthy until the follow- 

 ing May and June. It then begins to change to a pale green and 

 later to yellowish and brown. By the time all of the foliage is dead, 

 about the 1st of July, the overwintered broods of beetles begin to 

 emerge. By the middle of August most of them are out of the dead 

 trees and have entered the living ones. 



This is by far the most destructive insect enemy of the pine within 

 its range, and under present conditions is a constant menace to the 

 forests of matured or merchantable-sized timber. It can be con- 

 trolled hj felling the infested trees and by removing the infested 

 bark from the main trunks without burning the bark or tops. This 

 work must be done during the period between the 1st of October and 

 the 1st of July to destroy the broods of the beetle before they emerge. 

 AMienever the timber can be utilized the product will pay all ex- 

 penses. If it has no commercial value it will cost on an average 



