CHAPTER IX.

Insects; general Characteristics of; Changes of; Prevalence of.-Means of Defense and Offense against them.

INSECTS.

INSECTS, in general, complete the round of their life, or rather lives, in one year. There are some exceptions, however, as the well-known seventeen-year locust, and also some three and four year insects, as the saperda, the May-bug, and the spring beetle or snapper, parents of the apple-tree borer, the corngrub, and the wire-worm. But, whether the period in which their changes occur be short or long, they are all definitely effected. The young are hatched, or the insect wakes from its torpor at the time of the opening of the leaves or flowers upon which they have to feed; and if, from any cause, they hatch before their food is ready, they die, although this rarely, if ever, happens.

They are air-breathers, with varied apparatus for this purpose suited to their condition, and changing with it. In the larva, or worm state, they are commonly furnished with spiracles or breathing-holes along their sides.

Their digestive apparatus consists, as in the snipe or woodcock, of a single uniform tube. In its passage through this simple opening, their food is elaborated, and the colorless blood formed. This, in their system of circulation, is carried with regularity from tail to head, and back again, passing in its return through the respiratory tubes. While in the larva or worm state, they are voracious and generally injurious. They eat, and digest, and spin through their allotted time, all the individuals of the same kind having equal life, however varied the limit of life in this condition may be in the different species. At the close of this definite period they take the chrysalis form, changing their appearance, structure, and mode of existence.

Having completed their organization and growth in the

chrysales, they become, by a curious metamorphosis, moths or butterflies; they are entirely harmless to vegetation, not chewing, but sucking their food; and after living a few days to perfect and deposit their eggs, they perish. Of those species which assume the form of beetles, having cutting or biting apparatus, some are injurious both in the state of larvæ and when winged. These do not spin cocoons, but the naked worm or grub passes through a state of torpor and change in the earth. Most kinds of insects have periods, recurring at longer or shorter intervals, in which they are unusually abundant and destructive, becoming in a single season a scourge to neighborhoods or nations, and again declining to their ordinary numbers. They also vary greatly with climate, locality, and crop, each of these having its peculiar general classes or species. The soft, slimy insects, as the slug and snail, which are the pests of the garden in moist and foggy island climates, are scarcely known under our bright summer sun, except in peculiarly wet seasons; and many of the insects of hot southerly latitudes disappear as we go north or rise high above the level of the ocean, or are found, like summer visitors, only in the heart of the season. In swampy lands, or by rivers, we find insects that do not frequent the dry uplands; in sandy localities, those from which clay soils are exempt.

The pea-bug is not found in corn, nor the wheat-fly in Lima beans, nor the parsley-worm upon the cabbage, but each adheres to its appropriate plant or class of plants. Some, however, take a wider range in their depredations. The rose-bug attacks indiscriminately the blossoms of the rose, the peony, or the grape-vine, the leaves of the oak, the elm, or the linden, and the fruit of the cherry, &c.

Insects that infest or injure garden vegetables, however, do not materially differ south and north, but are found in all latitudes in their specific seasons. In general, they belong to the crop and the season rather than to the particular latitude, a single wet, cool season producing multitudes of the softer slimy insects, which a bright hot summer prevents or destroys. Most species of winged insects, on the contrary, are born and rejoice in the sunlight, and many larvæ, as the nest-worm and others

of the caterpillar tribes, are stimulated to their most lively voracity by the bright heat.

The remedies prescribed in this work will be found, in general, to apply to classes of insects rather than merely to single species, and may therefore be made available in any locality.

The first care of the cultivator should be to make himself accurately acquainted with the formation, character, and habits of those varieties of insects which his climate or locality may produce, or which his crops invite, particularly their times of first appearance and subsequent changes. Upon such knowledge, well applied, he may often find the profits of his labor depending. It is as necessary to him as the diagnosis of disease to the physician.

The known and reliable means of defense from the ravages of insects are very limited. The field of patient and intelligent observation and experiment in this department remains comparatively unexplored, and may be entered with abundant prospect of reward by any one of my readers.

There are, however, a few points which it may be useful to mention.

1st. Insects have natural enemies in the parasites, or ichneumons, that deposit their eggs in the body of the insect or its larva, or in the chrysalis. In these living nests the young interloper is hatched, and lives upon the substance and destroys the life of his victim. These hidden foes, of which it is probable each variety of insect has at least one, are always present, always active, and can not be eluded. Others war openly, as the short yellow worm, the larva of the syrphus, that lives upon the cabbage aphis, blind, but always following his prey; also the numerous aphis-eaters, as the larvæ of the spotted or "lace-winged" and "golden-eyed" flies, and the ladybug, both in the larva and perfect state. These natural enemies we can transfer from plant to plant when necessary, thus putting them upon the track of their prey.

Among larger insects, their foes are the dragon-fly or darning-needle, and especially a smaller blackish fly, looking like a cross between a dragon-fly and wasp, which hunts for his food with the activity and intelligence of a terrier. The birds, also,

and the bat live largely upon insects, which they consume both in the larva and the winged state, and the toad, though not a spry hunter, can often and expertly catch a fly.

Moles, also, and some ground-beetles destroy the various grubs that are hatched or harbored in the earth.

Some insects have protectors. Ants are said to guard the aphides, and, by a peculiar process, milk them, or, perhaps more truly, by a startling threat, to rob them of the sweet juices they suck from plants.

2d. We have also opportunities for escaping their depredations by changing a little the period of sowing or planting, though this also may sometimes expose us to other inconveniences.

Late-sown wheat has been found to escape, at least in part, the depredations of the fly or the weevil. Late-sown peas are not so liable to be punctured by the pea-bug, but they are peculiarly exposed to check and mildew from the heat, which by early sowing they would have escaped. But late-planted winter cabbages not only escape the cut-worm, but, if driven into. rapid growth by careful after-cultivation, are improved in quality by the delay.

3d. Insects have tastes and distastes, of which we may perhaps avail ourselves in self-defense. As they carefully avoid certain plants, we may mix these with those which they attack, and try thus to shield them. Onion, hemp, tobacco, and tomato have been suggested and recommended for the protection of cucumbers, melons, &c., on this principle. There is, however, a difficulty in the application of it. A single plant of either of the three last named in each hill, left to grow unchecked, will monopolize possession and destroy the crop; whether if kept closely trimmed they would effect the end, or whether, if they would, the labor could not be better applied, are questions to be answered. The onion, as well as several small herbs with strong odors, may be well worthy of trial. We have also some other means of offending them, which will be mentioned in connection with the several insects.

4th. We possess various means of injuring or destroying them. There are certain points in the history of insect life E

when we may successfully assail it, viz.: a. In the eggs, which, in nests of from ten to a hundred, we may gather by hand, or scrape from the trees on which they are deposited. b. In the chrysales or cocoons, which are often more easily found and gathered than the eggs. c. In the perfect or winged state, by means of fires in their season. d. For those kinds which make nests, the period of weakness immediately succeeding the hatching of the young colony, when they may be crushed at once. We possess also various other means of injuring or destroying them. Upon some we may sow lime or plaster with effect; others are destroyed by drenching with fatty or soapy matter, which kills them by stopping their breathing-tubes, or with water, which simply drowns them, as the palmer-worm has been found to be destroyed by violent rain. We may gather them by hand, or entrap them with sweets, and in various other ways. But to all this labor there is a limit of wisdom, which it is not worth while to pass. The general principle may be confidently adopted, that only those insects which attack healthy crops and cause disease will repay the trouble of cure or catching. The sole remedy, or rather preventive, for those induced or invited by disease, as the root-worm, the cabbage aphis, the cucumber striped bug, &c., is the preservation of vigor in the crop by timely and suitable culture. In more than thirty years' experience and observation, I have never known a healthy crop of cucumbers materially injured by the striped bug, nor a diseased or checked crop that escaped the bug, or that was restored by the destruction of its supposed destroyer.

In the following list of insects, all that are injurious to garden vegetables in every locality may not be included, but the number inadvertently omitted must be small, and such descriptions, and directions, and hints are given in regard to those enumerated as will perhaps furnish aid in reference to others that may have been left out.