40 STATE POMOLOGICAL SOCIETY. 



ful swing, I am not prepared to say. Very likely this habit was acquired 

 through the agency of natural selection, for certainly the insects would be safer 

 if they dropped at the shiver caused by alighting cherry-bird or oriole, and 

 would thus survive the perils by day while their less fortunate companions 

 would be exterminated. A habit would thus be formed which would aid the 

 larvae in their "struggle for life" and if it conferred pleasure at the same time 

 it would be still better for the insect. 



As to the kind of food perform! by the different larvae, there is some doubt, 

 though it is probably true that both species will live and thrive on apple, elm, 

 pear, plum, cherry, and linn. From the fact that in Cambridge, where pome- 

 taria is much the more common the elm is seriously defoliated, while here where 

 vernata seems most abundant, and perhaps the only species, the apple is more 

 subject to devastation, we might infer that the fall canker-worm preferred the 

 elm, while vernata chooses the apple. But we must not forget that in New 

 England the elm is far more common, as it is grown extensively for shade, and 

 is thus brought under immediate observation. In fact these drop-worms demand 

 attention as they drop by their silken cord and hang suspended just above the 

 side-walks to be borne off by the first passer-by, who very likely is ready to faint 

 at the sight of a worm. While with us the apple tree is far more cultivated 

 and far more subject to observation. This question needs farther investigation, 

 and it is a pleasing fact that we may all contribute our mite in the work of ob- 

 taining the desired information. Late in June these larva? spin a cord by means 

 of which they swing to the ground, which they at once enter to the depth of a 

 few inches ; vernata to form its earthen cocoon with a silken lining, in which it 

 may rest as a chrysalid till the next March; while pometaria weaves its cocoon 

 of silk, incorporating but little earth, taking more pains than vernata, even 

 though it remains in its pupa state only about one-half as long. 



Thus with the natural history and habits of these destructive pests before us 

 •we are quite prepared to successfully consider the subject of 



REMEDIES. 



It will be seen at once that we have several lines of attack by which we may 

 hope to overcome this canker-worm evil. We are not compelled, as with that worst 

 enemy of the pomologist, the codling moth, to limit our fire to a certain time or 

 to a single stage of the insect's development. We may seek to destroy the 

 pupae while they are "quietly biding their time" snug in their cocoons; we 

 may essay to prevent the wingless female from passing into the tree; we may 

 make war upon the eggs before they hatch; or, if all other precautions have 

 been neglected, we may still hope to rout the enemy even after the larva? have 

 commenced their attack. 



HOW TO DESTROY THE CHRYSALIDS. 



We have seen that the canker-worms, both vernata and pometaria, go a few 

 inches beneath the surface of the ground* to pupate, — vernata in a fragile 

 cocoon to remain as a chrysalis till March, while pometaria constructs a firmer 

 cocoon wherein the inchoate insect abides till October. Hence, we have not 

 far to seek that we may find a good and sufficient means to nip the evil 

 while yet in the bud. To accomplish this the ground beneath the affected 

 trees should be plowed in August or September, which of itself will prove fatal 

 to very many of the pupae, especially with vernata, whose fragile cocoons will 

 be very generally broken, and Prof. Riley has shown that they seldom survive 



