Rensselaer Union, Volume 7, Number 43, Rensselaer, Jasper County, 15 July 1875 — Increase of Noxious Insects. [ARTICLE]

Increase of Noxious Insects.

It must be quite apparent to every careful observer that noxious insects are on the increase in all parts of the country. We do not suppose that new species are being created to annoy us, but simplythat circumstances have been favorable for the development and multiplication of those which have existed in past ages. For instance, the Colorado potato beetle is no new creation, for it has doubtless existed on the Western plains and mountains ever since its natural food plants came into existence. But its numbers, as late developments, have shown, were limited in proportion to the amount of food produced in those regions, and it was only when man presented in our domesticated potato a larger supply that it began to multiply to any considerable extent. We may also conclude that the quality of food obtained in the potato is superior to the wild solanums , which presents another cause of rapid increase. In this instance, as in hundreds of others which might be named, plants improved by domestication and cultivation are far more acceptable food to insects than those in their wild or natural state. It is well that our farmers and fruit culturists should consider this question of “ food plants” in order to more fully understand why certain kinds of insects increase to an alarming extent when all other conditions except the sole one of food have remained unchanged, or at least been but slightly disturbed. The common plum curculio destroys the domesticated and improved varieties of the plum over a very wide range of country, and will not attack the wild varieties unless compelled to do so by a scarcity of the better sorts. No one can for a moment doubt that this insect formerly bred in the fruit of the wild plum; but, like ourselves, it' prefers the improved varieties. The same is true of the codling moth and various other insects which attack the apple; hence the multiplication and improvement of fruits tend to increase the opportunities and facilities for a larger number of noxious insects. A total abandonment of the culture of certain kinds of fruits would not be likely to exterminate their insect enemies, because there are usually wild varieties or closely-allied species which would answer the purpose of food. Of course .we may lessen the number by decreasing the quantity of food plants; but total annihilation of a species of noxious or beneficial insect is a very difficult accomplishment through the direct efforts of mankind. Not only have we furnished to noxious insects food to aid in multiplying, but in our ignorance we have disturbed the natural conditions which insure an equilibrium between the noxious and beneficial species through the ever-continued war of races. In addition to this disturbance of natural laws, w r e are, as a people, as likely to destroy our insect fiends as foes if we attempt to do anything in this direction. Entomology is not taught in our common schools or colleges —at least not to an extent to be of any practical use to the masses, and the result Ik general ignorance upon this important subject Many of the most beneficial species are large and conspicuous, and consequently the most likely to be destroyed by those who make war indiscriminately upon anything and everything of the kind. There are thousands of minute parasitic insects which destroy those of larger size; but in the general neglect of entomological science Jhey have been overlooked, and their value to man is little more than fuessed at. Ninety-nine persons in a hunred in finding one of the common green tobacco or tomato worms infested with parasites would crush it, while the healthy specimens might be passed unnoticed. Now, a well-known minute parasitic fly attacks these worms, as they are called, although they are properly the larvae of the five-spotted pliinx, a large moth frequently found flying around at night. The fly deposits her eggs in the black larva, w'here they feed upon the flesh between the skin and vital parts, never entering the latter, as this would kill the victim too soon for their purpose. When the larva of the fly attains its maturity, it comes out upon the surface, and there spins itself a small white cocoon of gossamer fineness. These cocoons being fastened to the skin by one end standing erect, and of course quite conspicuous, would consequently attract the- eye of anyone looking for worms. Such infested specimens should never be injured, because they are sure to die, and the parasites, if left to themselves, will continue the good work of destruction. The green cabbage-worm, which has made such fearful ravages durng the past half-dozen years is now rapidly disappearing under the attacks of a similar parasite, which has followed these pests from their home in Europe. By knowing the habits of the various species of insects, as well as their enemies, we are frequently enabled to combat them successfully; otherwise our efforts to destroy are of no avail. Our friends, the insect-eating birds, have also been ruthlessly destroyed in all parts of the country, and a war of extermination is still going on in communities where we might expect better things. These are but a small number of the causes which might be named, all working together in giving the noxious insects the advantage over the husbandman, and bringing disastrous results where good would come if an opposite course had been pursued.— N. Y. Sun.