SB 

 818 

 C578 

 ENT 



Circular No 9, Second Series. 



United States Department of Agricnlture, 



DIVISION OF ENTOMOLOGY. 



CANKER-WORMS. 



Fig. l.—Paleacrita vernaUi : r(, male moth ; 

 6, female moth — both natural size ; c, joints of 

 female antenna ; d, joint of female abdomen ; 

 e. ovipositor — enlarged. (From Riley.) 



GENERAL APPEARANCE AND METHOD OF WORK. 



Shortly after the apple tree has put forth its leaves in the spring large numbers 

 of a slender, naked span-wonn, or measuring worm, sometimes appear upon 

 this and various other kinds and orna- 

 mental trees, in the leaves of which 

 they gnaw small holes. As thej' in- 

 crease in size, the entire leaf, with the 

 exception of the stout midrib, is de- 

 voured. Two different insects are often 

 concerned in this destructive work 

 namely ; the fall canker-worm, repre- 

 sented at Figure 4, and the spring 

 canker-worm, shown at Figure 2. The 

 latter will be readily distinguished by 

 possessing only two pairs of legs on the 

 underside of the posterior half of the body, tlieve being three pairs in the species 

 first mentioned. Both are evidently natives of this country, and have never 

 been reported as occurring outside of North America. 



THE SPRING CANKER-WORM. 



{Palcacvita, renintu Peck.) 



Distribution. — This is the species usually concerned in the widespread dcfnliatitm 

 of fruit trees, particularly in the Mississippi valley and throughout the West. It 



ranges from Maine to Iowa, and southward to Texas, 

 Init is more restricted along the Atlantic seaboard, 

 wliere it has not as yet been reported as occurring 

 south of New Jersey. Owing to the fact that the 

 adult female insects are wingless, the sj^read of the 

 si)ecies is necessarily slow, and is principally ac- 

 conii)lislied through the medium of nurscny stock in- 

 fested with the insect's eggs. 



Natural history and habits. — Although tlu' females 

 are wingless, the males are furnished with two pairs 



Fig. 2. — Palencritn ve.rnatd, : 

 a, larva— natural size ; 6, eggs- 

 natural size .and enlarged; c, 



side view of segment of larva ; of rather large, thin wings; the general color is 



d, dorsal view of same — both 

 enlarged. (From Riley.) 



l)luish gray, with light and dark markings, as shown 

 at Figure I, a. Dviposition sometimes occurs during 

 mild winters, but as a general rule not until March or April. The eggs 



