THE SPRINC4 CANKER-WOKM. 19 



shell beconiiiiii- more or less cotioavo c'entralh\ Shortly before hatch- 

 ing the eggs become (niite dark, due to the color of the larva within. 

 Eo-gs secured from females in confinement on the nights of March 

 8, 10. and 1'2. and kejjt undci- out-of-door conditions in the insec- 

 tarv yard at the I)ei)artment of Agriculture, "Washington. D. C.. 

 were hatching April 10. 11. and 14, respectively, giving for this stage 

 a fairly uniform i)eriod of thirty-two to thirty-three daj^s. The 

 effect of warm weather ui)()n the development of the embryo may be 

 judged from the fact that eggs kei)t in the insectary at a tem])erature 

 of 05 to 70° F. hatched in aI)ont eleven and one-half days. 



"When just hatched the si)ring canker-worm is quite small, measur- 

 ing but 1.25 to 1..") mm. in length, varying with the extension of the 

 body. The head is aljout 0.2."> nun. wide, which slightly exceeds the 

 width of body across thoracic segments. The head and shield are 

 shining black, and the body above dark olive-green, with a distinct 

 central hmgitudinal white stripe centered with narrow interrupted 

 lines of the same color as the body. Along each side is a wide irregu- 

 lar white stripe, including the spiracles and adjacent tubercles. 

 Below, the body is dark yellowish or brownish in color. The thoracic 

 legs are stout and dusky exteriorly. There is a single pair of pro- 

 legs on the sixth abdominal segment and a pair of anal i)rolegs. 



The larva' come from the eggs about the time the leaves of the 

 apple are pushing out, and the latter are at once attacked. At first 

 only small holes are eaten through the leaves, but later, as the larva? 

 grow, the entire leaf substance save the midril) is devoured. (See 

 PI. III. figs. (•>, T.) 



After three or four weeks of feeding, the time varying nuich with 

 the temperature, the larviv have become full grown. They then meas- 

 ure from 18 to 2o nnn. (0.7 to 0.9 inch) in length. Considerable 

 color variation is likely to occur, some specimens being ash-gray, 

 green, or yellow, but the predominating color is dark greenish olive 

 or blackish. There are two pale narrow lines down the back, centered 

 with a broader dark strii)e and a whitish stripe along each side. 

 (See PI. Ill, fig. 2.) The larva of this species is readily distin- 

 guished from that of the fall canker-worm by the fact that the former 

 has but two pairs of prolegs, while the latter has three, the first pair, 

 however, on the fifth abdominal segment, being more or less reduced. 



Newly hatched larva' placed on apple trees under a large wire 

 cage in the insectary yard April 12, lOO."), had matured and were 

 entering the ground for pupation by Ma_y 8, and by May 11 all had 

 disappeared from the trees. This gives twenty-seven to thirty days 

 for the larval existence. The egg and larval stages together require 

 some two months, and the remainder of the year, except the time 

 spent in the adult condition before ovipositing, is passed in the pupal 

 stage in the soil. As has been stated, the insect pupates from about 



