AN AGRICULTURAL REVOLUTION. 



641 



ing a dwarfing and malformation that are very vexatious to the 

 horticulturist. An apple thus damaged is shown in Fig. 3. 



The eggs of the curculio are deposited beneath the skin of the 

 fruit, and the larvae remain concealed until full-grown. Conse- 

 quently the early stages of the insect can not be reached by spray- 

 ing. Fortunately, however, the parent beetles can be killed before 

 many eggs are deposited, by sparsely coating the foliage and fruit 

 with poison from the spraying machine, and thus the plums will 

 be saved. The practicability of this has been proved repeatedly 

 by commercial orchardists. 



In addition to the insects affecting orchard fruits, there are 

 hosts of enemies to the foliage. Nearly all of the latter, fortu- 

 nately, are also open to destruc- 

 tion by means of the spraying ma- 

 chine. The canker worm is one 

 of the most destructive of these 

 foliage pests ; at occasional inter- 

 vals during the last century it has 

 denuded thousands of orchard and 

 shade trees-in many parts of Can- 

 ada and the United States. Its 

 different stages are shown in Fig. 

 4. The damage is done by the 

 worms or larvae which hatch from 

 masses of small cylindrical eggs 

 (e), usually deposited upon the 



bark of the trees. These larvae feed upon the parenchyma of the 

 leaves, and sometimes cause a badly infested orchard to appear 

 brown and seared, as if scorched by fire. They continue feeding 

 for several weeks before becoming full-grown. Then they descend 

 to the ground, burrow into the soil a short distance, and spin 

 silken cocoons within which they change to the pupa or chrysalis 

 state, remaining in this condition a few weeks, when the moths 

 come forth. The two sexes of these moths differ greatly : the male 

 (a) has large, well-developed wings, while the female (b) is wing- 

 less. The latter is of an ash-gray color. On emerging from the 

 chrysalis she crawls to the base of the tree and ascends the trunk 

 some distance ; here the male finds her, and, after mating, she 

 deposits her eggs on the twigs or branches of the tree. 



The canker worm, like nearly all similar leaf-eating cater- 

 pillars, is so easily destroyed by spraying that, while in years past 

 it was greatly dreaded by orchardists, it now inspires little fear. 



The three insects above mentioned are all examples of those 

 species having biting mouth-parts, and which in consequence 

 attack the plant by biting piece by piece the tissues of leaf, stem, 

 or fruit. It is on this account that they are open to destruction 



VOL. XLII. 43 



Fig. 4. — Canker Worm : e , eggs ; ,/, larva ; 

 g, pupa ; (?, male moth ; A, female moth. 

 (After Kiley.) 



