18 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



Complaints of )>oth fall and .spring canker-worms are frequently 

 received by the Bureau of Entomology. Correspondents often report 

 that they 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 sprays. 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 readily killed by thorough use of poisons. In most cases the 

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

 ough applications of the spra}', the large size of the trees and the 

 unfamiliarity of the orcharclist with spraying operations often con- 

 tributing to this end. 



In the present l)rief article the life history and habits of the spring 

 fanker-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 

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

 the fall. The operations of spraying and plowing herein discussed 

 Avill be equally effective in its control. 



LIFE HISTORY AND HABITS. 



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

 obtaining their groAvth 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 pupse (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, Mhich 

 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 ovipositing 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 was 

 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 111), with an average for 1'2 masses of 47. 



An individual egg is elongate-elliptical in outline, somewhat 

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

 I'ecently deposited eggs were found to be 0.G9 by 0.42 mm. When 

 first deposited the surface is shining, pearly white, 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- 



