17 



the White-spotted Tussock-moth, and the Canker-worm, in all of 

 which the female is destitute of wings. The Canker-worm appears to 

 have been first known as a noxious insect in New England, but it has 

 now become spread over all the Northern and Western States, as far 

 west as Iowa, and as far south as Missouri. I have received, the past 

 season, accounts of serious damage done by them from Clinton, Wis- 

 consin, and DuQuoin in the southern part of Illinois, and from several 

 intermediate places. Reports of their injuries have also been com- 

 municated to the Department of Agriculture at Washington from 

 Norfolk county, Massachusetts; from several counties in Ohio, and 

 from Jefferson county in Iowa. In these communications they are 

 sometimes designated as the Measuring-worm, and sometimes as the 

 Black span worm. But, as might be expected from the wingless char- 

 acter of the females, their distribution is very unequal and apparently 

 arbitrary, a common road sometimes serving for years as a barrier be- 

 t ween a free and an infested orchard." 



DESCRIPTION*. 



" The moths are of a pale gray color, and have no conspicuous mark- 

 ings. The wings of the male are of a very thin and flexible texture, 

 and are usually seen more or less denuded of their scales. The 

 females, as already stated, are wingless. They vary in length from two 

 to five-tenths of an inch. Their color is produced by short black hairs 

 and scales, on a whiteish ground. The thorax is hoary, usually with 

 a distinct transverse black line or narrow band. Some individuals 

 have a distinct black dorsal stripe extending the length of the body, 

 but this is usually interrupted, and often obsolete, or wanting. Their 

 general color is so similar to that of the bark of the apple tree that 

 they are easily overlooked when not in motion. The proboscis is ob- 

 solete in both sexes ; and these insects take no food in their imago- 

 state. 



" The natural history of these insects may be briefly stated as fol- 

 lows : The female deposits her eggs upon various trees, but mostly 

 upon the apple trees and the elm. These eggs hatch the latter part 

 of April or beginning of May, or at about the time of the flowering of 

 the red currant — the time varying a week or two, according to latitude 

 and character of the season. The caterpillars feed upon the foliage, 

 and are often so numerous as to desolate whole orchards of apple trees 

 or whole parks of elms. They attain their full growth in about one 

 month, when they let themselves down by a thread, and burrow from 

 two to six inches into the ground. There they assume the chrysalis 

 state, and remain, with a few exceptions, through the winter, and 

 until the first mild weather of spring releases them by removing the 

 snow and frost from the surface. They immediately make their way 

 to the nearest tree and crawl up its trunk. The winged males are 

 now seen fluttering about the wingless females, and, after pairing, the 

 females deposit their eggs and perish, thus completing the circle of 

 their existence. 



" The female'canker-worm moths differ much in size, varying, as we 

 have stated, from two to five-tenths of an inch in length, and the 

 number of eggs laid by eaoh individual varies accordinglv. I have 

 e— 2 



