200 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



2 to 3 inches. The males are smaller, with the front wings 

 dark gray and the hind wings yellowish red lined with black. 

 The mature larvae are about 2 1 2 inches long, somewhat pinkish, 

 with a dark head and with scattered hairs arising from small 

 brown spots on the body. Eggs are laid in June and July, each 

 female depositing from 200 to 300 in cracks and crevices or on 

 the smooth bark of the host tree. The larvae mine in the sapwood 

 and heartwood of trunk and limbs and cause injuries that show 

 up later as defects in the lumber. Completion of the life cycle 

 requires 3 years. 



Another species, Acossus populi Wlkr., does similar work in 

 poplars and cottonwood. Givira lotta B. & McD. works in the 

 outer heavy bark at the base of ponderosa pines in Colorado. 



CLEAR-WINGED MOTHS 



Many species of clear-winged moths or pitch moths belonging 

 to the family Aegeriidae work in the inner bark and bore into the 

 wood of various forest trees. An exceptionally large number of 

 them work in the wood of broadleaved trees and at times so riddle 

 the interior that the limb or tree dies or is broken off by the wind, 

 and the products derived from the wood show serious injuries. 

 The adults of this group are very pretty clear-winged moths, re- 

 sembling hornets. The caterpillars are naked or have only a few 

 prominent hairs. So many species are seldom seen by the forester 

 that no attempt will be made to list all of the western species here. 

 The alder borer (Thamnosphecia americana (Beut.) ) is sometimes 

 found working in alder. The locust clearwing {Paranthrene ro- 

 biniae Hy. Edw.) sometimes is very injurious to locust and poplar. 

 The cottonwood crown borer (Aegeria tibialis pacifica (Hy. 

 Edw.)) infests cottonwood, poplar, and willow, as does Aegeria 

 apiformis (Clerck). Ramosia mellinipennis (Bdv.) attacks syca- 

 more and oak in California. 



HORNTAILS, OR WOOD WASPS 



The horntails, or wood wasps (Siricidae), are injurious to the 

 green, unseasoned, or moist wood of practically all western coni- 

 fers. Frequently serious damage is done, especially to the wood of 

 fire-killed trees. Sometimes redwood lumber is attacked and in- 

 jured, even after it is cured and placed in storage yards. 



The adult females are thick-waisted, cylindrical wasps, with two 

 pairs of wings and a hornlike ovipositor, which resembles a 

 stinger, at the rear of the abdomen. They are usually of metallic 

 colors — dark blue, black, or marked with orange and red. The 

 females alight on freshly felled injured or dying trees and with 

 great dexterity insert their long flexible ovipositors deeply into the 

 wood, often for an inch or more, and lay their eggs. Sometimes 

 they are unable to extract their ovipositors from the wood and 

 die in this position. The larvae are cylindrical and yellowish white, 

 with a small spine at the posterior end of the body, and they 

 sometimes hold their bodies in the shape of a shallow letter S. 

 They are truly wood-eating in habit and work in the solid wood 

 without any opening extending to the outside. As they feed they 



