18 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



Coiui)laints of both fall and spring canker-wonns are frequently 

 received l)y the Bureau of Entoniologv. Correspondents often report 

 that the}' are unable to protect their trees by the use of arsenicals, and 

 the opinion has at times been expressed that these insects can not be 

 destroyed by arsenical sj^rays. While it has often been stated in the 

 literature on canker-worms that they are more resistant to poisons 

 than many other species of insects, yet there is no doubt that they 

 may be readih^ killed by thorough use of poisons. In most cases the 

 poor results from spraying are evidently due to failure to make thor- 

 ough api^lications of the spray, the large size of the trees and the 

 unfamiliarit}' of the orchardist with sj^raying operations often con- 

 tributing to this end. 



In the present brief article the life history and habits of the spring 

 canker-worm are given, together with results of practical work in its 

 control. The life history and habits of the fall canker-worm prac- 

 tically parallel those of the spring species, except that the great 

 majority of the moths of the former species emerge and oviposit in 

 the fall. The operations of spraying and plowing herein discussed 

 will be e(jualW effective in its control. 



LIFE HISTORY AND HABITS. 



There is but one generation of canker-worms each year. After 

 obtaining their growth on the trees in the spring, the larva enter the 

 soil to a depth of from 2 to 5 inches, and after making an earthen 

 cell transform to pupae (see PL III, fig. 3), in which condition they 

 remain until the following spring. Early in the spring, or even 

 during warm spells in winter, the pupae transform to moths, which 

 make their escape from the soil and go to the trees. The males are 

 winged, as shown in Plate III, figure 5, but the females are destitute 

 of wings, as illustrated in Plate III, figure 4. In ovij^ositing the 

 females climb the trees and place their eggs in irregular masses under 

 loose bark scales, in cracks in the bark, in crotches of limbs, etc., as 

 shown in Plate III, figure 1, which illustrates an egg mass which Avas 

 placed on the underside of a bark scale. The number of eggs in an 

 individual mass varies greatly. Females taken presumably before 

 oviposition had begun deposited eggs in confinement, the number to a 

 mass varying from 17 to 119, with an average for 12 masses of -tT. 



An individual Qgg is elongate-elliptical in outline, somewhat 

 resembling a hen's egg in miniature. The average dimensions of ten 

 recently deposited eggs were found to be 0.69 by 0.42 mm. "When 

 first deposited the surface is shining, pearly Avhite, but in the course of 

 a few hours the egg takes on a yellowish-green color, in certain lights 

 showing a golden, greenish, or purplish iridescence. As the embryo 

 approaches maturity it becomes very evident and lies curled around 

 just within the shell, its cephalic and caudal ends together, the egg- 



