CAlifKER-WORM. 



101 



The practical advice given in this extract is by n® means devoid of 

 value, but the writer has fallen into the error of mistaking the chrysa- 

 lids of the insect for its eggs. 



But, like other widely spread noxious insects, the Canker-worm has 

 had its seasons of increase and decrease. It was very abundant in 

 Maseachusetts seventy years ago ; subsequently it became almost un- 

 knov/n in that State for many years. It is said to have disappeared 

 after a very heavy frost in the month of June which killed the cater- 

 pillars. But this is hardly probable of so hardy an insect as the Canker- 

 worm. They appear to "have been numerous in the vicinity of Boston 

 in the year 1840, and several preceding years ; but Dr. Harris states 

 that from i84rl to 1847 they almost disappeared from that section, but 

 that they rapidly increased again after the last mentioned date. 



It is remarkable that several of our noxious insects which are most 

 destitute of the means of locomotion, have become the most widely 

 spread over the country. This is the case with the Oyster-shell Bark- 

 louse, the White-spotted Tussock-moth, and the Canker-worm, in 

 all of which the female is destitute of wings. The Canker-worm ap- 

 pears to have been first known as a noxious insect in New Eng- 

 land, 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 by them from Clinton, 

 Wisconsin, and DuQuoin in the southern part of Illinois, and from 

 several intermediate places. Keports of their injuries have also been 

 communicated 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- 

 tween a free and an infested orchard. 



DESCRIPTION. 



The general appearance of this insect, in its several stages, is suffi- 

 ciently obvious in the figures at the head of this article. They are of a 

 pale gray color, and have no conspicuous markings. 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 wing- 

 less. They vary in length from two to five-tenths of an inch. Their 



