102 SECOND ANNUAL KEPORT OF 



ker-worm that was injuring his orchard. I told him that about fifty 

 years ago they had been in my father's orchard some six years, and 

 killed a large number of the trees ; that, we plowed it late in the fall, 

 and have never seen the Canker-worm there since. I advised him to 

 plow Ills orchard immediately. The next day he plowed it as far as 

 the worms had been in it. I received a letter from him a few weeks 

 ago, stating that the Canker-worms were not in his orchard this year, 

 and those trees that were- injured and not killed last year, revived 

 some this year. 



Now there is no doubt but late plowing wall produce somewhat 

 different effects, according to the character of the soil, and the depth 

 of the plowing ; but that it is more generally beneficial than other- 

 wise I am perfectly convinced, and as for the assertion of Mr. Wm. P. 

 Lippincott, of* Vernon, Iowa, made some time ago, in the Iowa Home- 

 stead, namely, that it left the ground full of harbors for the next year's 

 breeding, it suffices to say that the insect does not breed in the 

 ground, and, holes or no holes, the worms will penetrate the soil 

 whenever the time arrives to change to chrysalis. After the summer 

 months the insect invariably lies in the chrysalis sta,te snugty en- 

 tombed in a little earthen cell very thinly lined with silk, from two 

 to six inches below the surface. This cell, though frail, is a sufficient 

 protection, so long as it is whole, from any excess of moisture, and at 

 the same time prevents too much evaporation in case of summer 

 drouth or dry winter freezing. Now I have proved by experiment 

 that whenever this cell is disturbed or broken in cold weather, the 

 chrysalis has not the power to penetrate the ground again, and in the 

 great majority of instances, either rots, dries out, becomes mouldy, or, 

 if on the surface, is devoured by birds. Even summer plowing, if 

 performed after the first of July would work beneficially ; and it is for 

 this reason, that clean, well cultivated orchards are more free from 

 the attacks of this insect, than slovenly and neglected ones. The only 

 advantage oflate fall plowing, lies in the facts, that the chrysalis is at 

 that time too benumbed to work itself into the ground and form an- 

 other cell, and that birds are then harder pushed for food, and more 

 watchful for any such dainty morceau. 



As to the efficiency of hogs, in rooting up and devouring the chry- 

 salids, during the summer months, abundant favorable testimony 

 might be cited ; but the facts are too obvious to need argument. 



ENEMIES OF THE CANKER-WORM. 



Like most of our noxious insects, the Canker-worm is subject to 

 [Fig. 63.] y ie attacks of cannibal and parasitic insects. It is 



also devoured by very many different birds, some of 

 which almost entirely live on it; and Dr. Packard, 

 of Salem, Mass., has observed an elongated mite 

 (JYolhrus ovivorus, Fig. 68, enlarged) devouring its 

 eggs. The most common parasite which I have yet 

 discovered with us, is an undescribed small four- 

 winged fly belonging to the genus Microffaster, of 

 the same size, but differing from the Military Micro- 



