North. It is the "alfalfa worm" of Kansas and Nebraska and elsewhere it is simply called the army worm. Its technical name is Laphygma frugiperda.

It will thus be seen from the examples cited that the popular name of an insect has frequently little bearing on its identity. The scientific name must be determined.

A frequent source of injury to plants is due to contiguous growers who raise the same, or similar crops, for different purposes, e. g., some may raise cucumbers for pickling, and in the immediate vicinity others grow melons for fruit, so that pickle-growers pick their crops while quite young, and the fruit-growers when older. This means that after the picklegrower has stopped pickling, numerous vines remain, and the insects scatter from them to melon fields.

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Spraying Potatoes in Western New York [Photo by courtesy New York Experiment Station]

Insects Injurious to Vegetables

CHAPTER I

VALUE OF A KNOWLEDGE OF ENTOMOLOGY

GENERAL CONSIDERATIONS

FOR an intelligent understanding of the subject of insect control by agricultural practice one must know not alone that certain conditions produce an increase or decrease of certain forms of insects, but how this is accomplished, why the alternation of one crop with another is apt to result in insect injury, and why a system of crop rotation that would be of value in the control of one class of insects might be ineffective against another; how fall plowing, though destructive to one species, would not affect a different insect, and so on. In short, a knowledge of economic entomology beyond the fact that arsenicals are the proper remedies for mandibulate or chewing insects, and that kerosene will kill aphides or plantlice, scale insects, and other soft-bodied insects, is a prerequisite to intelligent effort in the control of noxious insects. Before we can hope to avert losses we must know what our insect enemies are, what species are destroying each crop, which ones are responsible for primary injury, which are secondary or merely auxiliary, how injury is accomplished, when injury begins each year, when it ends, as well as other facts.

Similarly desirable is it to be able to recognize useful insects, such as ladybirds, syrphus flies, tachina and ichneumon flies and other parasites, that these may not be unnecessarily destroyed, but, if possible, encouraged in their useful work.

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The different stages of some insects are so diverse that they can be identified only by specialists, and many entomologists are unable to recognize them without reference to technical descriptions and illustrations. Some knowledge of the distribution and origin of a species is of value, as well as some acquaintance with its history and literature.

A knowledge of the life history of an insect consists in knowing: when, where and how its eggs are deposited; how the larva feeds, and how many stages there are in this period; the habits of the larva, whether diurnal or nocturnal, whether omnivorous or a dainty feeder; how and where it transforms to pupa; how and where and in what stage it passes the winter; the number of generations produced each year; the first appearance of the insect and its disappearance, and the same of each generation; its food plants, natural and cultivated, and above all, its favorite foods, both as larva and adult. If to this we add a knowledge of the effect of farm practice and of insecticidal and mechanical methods on the insect we have, in a general manner, the main facts desired.

We must determine in what stage and at what time the insect is most vulnerable, and by practice and experiment learn the best remedy. A knowledge of the appearance and place of deposition of the eggs will, in the case of some species, furnish means for their control, for many insects can be combatted successfully merely by destroying the eggs. Others may be killed in their cocoons.

The most valuable weapon that can be used in combatting an insect consists in an intimate knowledge of the insect itself and its life economy, its natural enemies, its susceptibility to natural influences, heat and cold, dryness and moisture, and their effect upon its increase or decrease directly, or indirectly by destroying or favoring the growth of its enemies. A knowledge of the weeds and wild plants that furnish food for these insects, in addition to cultivated plants, and the soils in