72 IMISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



THE SATIN MOTH 



The satin moth {Stilpnotia salicis L.) {10) is a very injurious leaf- 

 eating enemy of poplars and willows. This moth, which is native 

 to Europe, was first reported in 1920, both in New England and 

 British Columbia. Since then the British Columbia introduction 

 has spread throughout western Washington and into Oregon. It is 

 a serious pest of planted shade and roadside trees, and may prove 

 destructive to native poplars and willows. 



The adults are large white moths with a satiny luster, a wing 

 expanse of approximately 1% inches, black eyes and legs, and a tuft 

 of hairs at the tip of the abdomen. The full-grown caterpillars are 

 about 2 inches in length, black with white markings on the sides, a 

 row of nearly square white marks along the back, and with brown 

 spines and long hairs. 



There is but one generation a year. During the flight of the 

 moths in July eggs are laid on trees or other objects in oval patches 

 covered with a white, satiny secretion which glistens in the sun. The 

 young larvae feed for a short time and then spin small cocoons or 

 hibernacula in bark crevices, where they pass the winter. Feeding 

 is resumed in the spring, and the larvae reach maturity in June. 

 Pupation occurs in loosely woven cocoons attached to leaves or other 

 objects. 



It was introduced without its European parasites, but it is at- 

 tacked by several native enemies, including tachinid flies, parasitic 

 wasps, sarcophagid beetles, mites, and birds. Some of these have 

 proved very effective in holding it in check. From 1929 to 1934, 

 five species of parasites of European origin were colonized and lib- 

 erated in Washington. Four of these have become established and 

 at least one, ApanteJes solitarius Katz., has become abundant enough 

 to show^ apparent effect. 



Direct control is obtained by spraying the trees in the spring with 

 a stomach poison such as lead arsenate. Wlien Qgg masses are 

 exceptionally abundant they should be treated with creosote. 



TENT CATERPILLARS 



(Malacosoma spp.) 



Tent caterpillars (78), which are responsible for the defoliation of 

 many different species of trees. and shrubs, can be recognized by the 

 large compact webs at the terminals of branches, which are such a 

 common sight during April and May. The various species are 

 indigenous to this continent, being widely distributed over the 

 United States. Outbreaks were recorded from Massachusetts as early 

 as 1646. Coniferous trees are sometimes attacked, but the preferred 

 hosts are deciduous trees and shrubs. Wliile large forest areas are 

 sometimes defoliated, the resultant damage is usually of no great 

 importance, since deciduous trees can readily recover from the loss 

 of foliage. 



The caterpillars that construct the tents are usually yellow to 

 brown, with rows of blue or orange spots and lines, and are lightly 

 covered with long hairs. A heavy, silk-lined cocoon is usually formed 

 in bark crevices or in leaves webbed together. The adults are tawny 

 yellow or brown motlis or millers and are frequently seen flying about 

 lights at night. 



