ANNUAL MEETING. 



37 



appeared at Marengo, Calhoun county, in 1863 ; since which time I have known 

 of their ravages at Plymouth, Wayne county, at Commerce and Pontiac, Oak- 

 land county, and now at Adrian, Lenawee- county. That they have made their 

 presence felt elsewhere among us is not improbable, though I have not been 

 advised if such is the case. So far as I have examined, and so far as I can 

 learn from others, it is the spring canker-worm, A. vernata, that works mis- 

 chief in the west, while east the fall species, the A. pometaria, is most common, 

 and hence the greatest pest. This opinion was sustained by a careful examina- 

 tion of specimens from Lenawee county, examined in February. As we shall 

 soon see, it is of great practical moment that we know which species is among 

 us, and as it is a question of easy solution, you may all render aid. It is a ques- 

 tion of no little interest, whether the canker-worms spread from some one 

 native spot, cast or south, as the Colorado potato beetle spread from the west- 

 ern plains ; or whether they come upon us from their forest haunts, perforce, 

 as their native food plants are sacrificed at the beck of civilization. The latter 

 view suggests itself, from the fact, as we shall soon see, that nature has placed 

 a serious impediment in the way of the rapid spread of these insects, coupled 

 with the fact that they make their appearance, ever and anon, in old orchards 

 many miles from any previous region of attack. This question can only find 

 solution in a wider and more careful research. 



Just now, — May 14, — I learn from Mr. F. F. Smith that a canker-worm, 

 very likely one of these species, is entirely defoliating the elms about Ionia. 



DESCRIPTION OR NATURAL HISTORY. 



The differences of these insects, which appear in the original descriptions, as 

 given by Prof. Peck and Dr. Harris, have been graphically set forth by Mr. 

 Maun and Prof. Kiley, in their papers already referred to. But let us first 

 note the points in which they agree : The general color of each is light gray or 

 ash color. The male expands about one and one-half inches, A. pometaria 

 being slightly the larger. The females are apterous, or without wings (see fig. 

 1 and 2, b), and nearly one-half an inch in length. Like all of this family, 

 the larvae (see fig. 3 a and 4/) are geometers, or measuring worms; that is, 

 they possess fewer feet than do most caterpillars, so that in crawling they are 

 obliged to loop or measure, hence the appellations loopers and measurers so 

 often applied to such caterpillars. Another family peculiarity is that of drop- 

 ping by a thread spun from their mouths, thus mimicking their distant rela- 

 tives the spiders, except that the spiders manufacture their silk at the opposite 

 extremity of the body ; hence the term drop worms. Both vcrnata and pome- 

 taria pupate in an earthen cocoon a few inches beneath the surface of the 

 ground. 



Let us next observe the differences between vernata and pometaria. In ver- 

 nata the antennae of both males and females are only forty jointed, while in 



pometaria they are over fifty jointed. In 

 the female of vernata (see fig. 1, c) they 

 are hairy, while they are smooth in the fe- 

 male pometaria (see fig. 2, c). The pri- 

 mary wings of the male vernata (see fig. 1, 

 a) are crossed by three black wavy lines, 

 often quite indistinct, while a fourth wavy 

 line of white crosses the wing still farther 

 out, which contains an oblique dash of 



'^tv?'' 



FIG. I, ANISOrTERYX VERNATA. 



a, male; b, female; c, antenna of female; e, 



ovipositor. 



