INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 



309 



THE SHOT-HOLE BORER OR FRUIT-TREE BARK-BEETLE 



Eccoptogastei rugulosus (Ratzeburg) (Family Scolytidse) ■ 



(Scolytw rugulosus Ratzeburg) 



(Figs. 304-307) 



Description. — The beetles are very small, nearly cylindrical in shape, 

 black exeept the tips of the wing covers and the legs, which are cinna- 

 mon red. They are about T V 

 inch long and one third as 

 wide. The larva 1 are slightly 

 longer than the adults, white 

 or dull yellowish-brown and 

 slightly curved. The pupa 1 

 are whitish, becoming darker 

 with age and about as large 

 as the adults. 



Life History. — In the 

 spring, April and May, the 

 adults of the overwintering 

 brood begin to emerge through 

 the small round "shot holes" 

 about T \ T inch in diameter, 

 which they make for this pur- 

 pose. After mating the 

 females make similar holes for 

 reentering the bark, beneath 

 which they carve large, 

 straight, primary burrows in 

 which, at various intervals 

 along the sides, they make 

 small pockets into which the 

 eggs are deposited. As the 

 eggs hatch the grubs make 

 small secondary burrows at 

 right angles to the primary 

 burrow. These larval bur- 

 rows are first very small, but 

 become larger as the larvae 



Fig. 303. — Barley stem showing slit and leaf 

 removed to show holes made by the snout of the 

 tide billbug, Sphenophorua discolor Mann. En- 

 larged twice. (After H. S. Smith. Photo by 

 author) 



grow and extend them, until when the larvae are fully matured, rounded 

 cells are formed at the ends where pupation takes place. From these 

 pupal cells the emergence holes are made through the bark. The eggs 

 hatch in about three days, the larvae mature in about twenty days and 

 the pupa 1 in ten days, making the summer life cycle about twenty-three 

 days. There are from two to three broods a year. The adults are 

 usually more numerous during the late summer. The winter is passed 

 in the larval and pupal stages under the bark. In southern California 

 the writer secured a number of living adults in the burrows in January, 

 indicating that some of the adults also survive the winter. 



Nature of Work. — The small, round holes in the bark of the trunks 

 and limbs of the trees give the first clue to the presence of this pest. 

 Upon removing the bark, the primary and secondary burrows or gal- 



