92 MISC. PUBLICATION 273, U. S. DEPT. OF AGRlCULTrPE 



■ Sawflies on Broadleaved Trees 



There are a large number of sawflies that feed on the leaves of 

 broadleaved trees. Some of these produce galls, and many others 

 feed externally on the leaves and cause a varying amount of damage. 

 Only a few will be mentioned here. 



The elm sawfly {Cinibex americana Leach) is commonly found in 

 the Middle West as well as in the Eastern States, but ranges west 

 into Colorado and British Colimibia. These sawflies are active feeders 

 on the leaves of willow and elm, and also attack poplar, alder, maple, 

 and other trees. The adults are large, steel blue to black, broad- 

 waisted sawflies about three-fourths of an inch in length with three 

 or four yellow, oval spots on each side of the body, short knobbed 

 antennae, and smoky wings. They girdle the bark on twigs and kill 

 many of them, especially in the tops of trees. The larvae are naked, 

 wrinkled, and pale yellowish with a median black stripe down the 

 back, ancl have eight pairs of prolegs. They usually lie coiled and are 

 from 1 to 2 inches long when full grown. The adults fly in May 

 and insert their oval eggs in the leaves. The larvae reach full 

 growth in July or August, and overwinter in cocoons in the debris on 

 the ground or just below the surface. Pupation occurs in the spring, 

 only a few days before emergence and flight. 



At least three other sawflies attack willow in the West. Cwibex 

 facifica Cress., which has similar habits to the preceding, is found 

 in Oregon and Washington, where the larvae feed on willow leaves. 

 The adults are large, about 1 inch in length, and are brownish red. 

 It is known as the Pacific sawfly. Cimhex rubida Cress, is found 

 in the sierras of California and Nevada and along the coast, feed- 

 ing on various species of willow. The adults are about three-fourths 

 of an inch in length, reddish brown, with black stripes on the abdo- 

 men and wings of metallic blue or smoky brown. Another species, 

 TncMosoma lanuginosa Norton, also feeds on willow in the Cali- 

 fornia and Xevada sierras. The adults, which are velvety or shiny 

 bluish black, with dense pale-yellow hairs on head, thorax, and base 

 of abdomen, look verj^ much like large bumblebees. They are about 

 three -eighths of an inch in length and have short knobbed antennae 

 and smoky brown wings. 



The Cottonwood sawfly {Pteronidea sp.) although common, has 

 not been identified specifically as yet. The larvae, which are slender, 

 about one-half inch in length, green, with brown head and black 

 eyes, and six pairs of prolegs on the abdomen, feed on the leaves 

 of black Cottonwood in northern Idaho. During the early feeding 

 period the larvae skeletonize the leaves, eating only the fleshy part, 

 but in the later stages of larval development the entire leaf is con- 

 sumed. ^^Tien mature the larvae construct small, parchmentlike 

 cocoons that are attached to the leaves. The complete seasonal his- 

 tory of this insect has not been determined, but it appears to have 

 one generation a year. 



LEAF BEETLES 



There are a number of beetles that are leaf eaters in the larval 

 or adult stage or in both. None of these have been responsible for 

 any noticeable injury to western coniferous forest trees, but the 

 skeletonizing and defoliation of broadleaved trees by beetles is a 



