appear. A fortnight later, they descend into the earth, and after remaining in the pupa state a fortnight, reappear as moths, flying all of September and October. The species ranges over the Southwest, West, and New England, and in Maine, as far north as a line drawn from Grand lake to Moosehead. Besides external enemies, it has seven internal parasites. The best way to kill out the worm is to burn meadows and grass lands, where the insect breeds, in the dead of the year.

GRAIN APHIS.

We now come to an insect whose transformations and habits are entirely different from those of the moth with its distinct larval and pupal stages; and eating nothing after the caterpillar is full fed. But instead, we have, hatched in the spring from eggs laid in the previous autumn, a plant louse of nearly the same form as in maturity; which by successive casting of its skin becomes a wingless female. No true larva and pupa state has been observed, though the insect may possibly undergo these changes in the egg.

We will suppose a number of eggs to hatch out their wingless females; with an occasional winged individual there are as yet no males in existence, and yet these virgin aphides or plant lice every few days produce hundreds of young, olive; each of which in turn come to maturity and produce their young alive. Hence, by the end of summer we have millions of lice over-running our wheat fields, the very youngest as well as the oldest as if for their lives sucking in the sap from the ear of the grain. For by a marvellous adaptation to their mode of life, what in beetles are jaws for biting, are here lengthened out, and joined together to form a tube, with a sucking stomach at the base. This tube the louse forces into the root of the ear, and thus anchored by their jaws, whole groups cluster head downwards on the heads of grain, and by their numbers color a whole field. But the supply of liquid food is greater than the aphides can manage, hence two tubes open out from the hind part of the abdomen, from which exudes a sweet sticky fluid called "honey dew." Ants come to eat it as it falls on the leaves, or lap it from the honey tubes of the aphis, and as the supply lessens, they gently strike the aphis with their antennæ to make them yield more.

At the approach of cold weather, when the whole race of aphides must be cut off, the virgin females produce winged individuals of both sexes, which after pairing, die out after depositing their eggs

for the spring brood. Our species may possibly be the aphis granaria of English authors, though a strict comparison of ours and the European species must be made before deciding whether it is an English importation.

Our species is oblong-oval shaped, narrowing toward the head, while the abdomen behind is swelled out and rather blunt at the end, with a rather long ovipositor in the female. Its color is green, covered often with a reddish brown bloom. The ends of the antennæ, the end of the shanks and thighs and the feet are black. In the young these parts are only smoky or dusky. Length of those with wings about one-tenth of an inch.

Dr. Fitch gives in the "Boston Courier," interesting observations on this aphis. Of its variation in color he says: "One of the most remarkable circumstances relating to these insects is the change in their color, which now began to take place. Whilst they were scattered about upon the leaves and stalks of the grain, they were of a bright grass-green color. Now orange yellow or deep flesh red individuals began to appear among them. This color is so wholly different from green, that these orange ones might be suspected to be a different species. But green females placed in vials were found next day to have young with them of both colors-some being green, others orange. And a few days later, other green females were found to have orange young only, no green ones being born any longer. It is probably the change in the quality of its food which causes the insect to change thus in its color, the juices which the plant elaborates for the growth of its flowers and seeds being much more highly refined, nutritious and dainty, than those which circulate in the stalks and leaves, where the insect first feeds. And it is truly curious and wonderful that this green colored insect, on coming to feed on the juices which grow the flowers, begins thereupon to give birth to young having a gray orange color similar to that of the flowers."

Dr. Fitch noticed several years ago in wheat fields, a green plant louse, though it was not common.

In East Hampden, Mass., "a plant louse of a pale brick red color was extremely numerous" in 1860; so also a "red insect" on the oats in New York was sent him. We thus know the insect we are to speak of was over-running the fields in some places, last summer.

Early in May last, when rye and winter wheat were but a few

inches out of the ground, I met with this insect more numerous than any other, in every part of every grain field in my neighborhood. Towards the close of that month, specimens having wings began to occur. By inclosing them singly in vials, I found that the winged females usually gave birth to four young lice in twentyfour hours, while those without wings produced eight within the same time."

The grain aphis became noticed the 18th July in New Jersey, then in the New England States. Probably very few farms in Maine escaped its presence. About the first of August it was noticed on a farm about thirty miles above Mattawamkeag, on the Penobscot. So on farms on the lakes that form the head waters of the Penobscot and Alleguash rivers, and on the Alleguash and St. John. I also heard of its occurrence in great numbers on the St. John, in New Brunswick. Like the army worm, while abundant on some fields, others were entirely free from its attacks.

The injury this aphis does, is to lessen the weight of the grain, which of course is a matter of great consequence. The constant draining of the sap that flows into the ear, causes it to be very light, if not withered and worthless.

Artificial means of driving off this pest have not yet been contrived. It has been suggested to kindle fires, throw on damp straw and let the wind carry the smoke over the field.

But the external enemies of this aphis are ready to help us. The lady bugs, coccinella, as larvæ and beetles, the golden-eyed flies, chrysopa, as larvæ, have been seen the past season in great numbers, in wheat fields, busily engaged in devouring the plant lice.

These minute insects have also their internal parasites, little ichneumons of the genus Aphidius. We have to go again to Dr. Fitch's article for information respecting their habits. "On many of the wheat heads, may at present [Aug. 6,] be noticed from one to a half dozen or more of these lice, which are very large, plump and swollen, of the color of brown paper, standing in a posture so perfectly natural, you suppose they are alive. Touch them with the point of a pin, you find they are dead. Pick off a part of their brittle skin; you see there is inside a white maggot doubled together like a ball. Put one or two of these wheat heads in a vial, closing its mouth with a wad of cotton. In a week's time, or less, you find running lively about in the vial, some little black flies, like small ants. These you see have come out from the dead lice,

through a circular opening which has been cut in their backs. Drive one or two of these flies into another vial, and introduce to them a wheat head having some fresh lice. See how the fly runs about them, examining them with its antennæ.

Having found one adapted to its wants, watch how dexterously it curves its body forward under its breast, bringing the tip before its face, as if to take accurate aim with its sting. There, the aphis gives a shrug, the fly has pricked it with its sting, an egg has been lodged under its skin, from which will grow a maggot like that first seen inside the dead swollen aphis. And thus the little fly runs busily around among the lice on the wheat heads, stinging one after another, till it exhausts its stock of eggs, a hundred probably, or more, thus ensuring the death of that number of these lice. And of its progeny, fifty it may be supposed, will be females, by which five thousand more will be destroyed. We thus see what efficient agents these parasites are in subduing the insects on which they prey. I find three different species of them now at work in our fields, destroying this grain aphis."

Now whether these insects will appear in such numbers in coming years, or again be rarely seen; and what are the causes of their great increase, we cannot tell. The army worm seems to be only an occasional visitor, and may not occur abundantly for several years. The aphis may be very troublesome for some years to come, and then gradually take its place among those insects which do each year considerable damage to grain. How to account for the sudden and marked increase of these or any other insects, once in five, twenty or fifty years, we do not know. Favorable or unfavorable seasons, the scarcity or abundance of parasites, and other physical influences that cause species to be rare or common in different seasons, do not satisfactorily to us, account for the fearful increase of the army worm and grain aphis in the summer of 1861.

GENERAL REPORT

UPON THE

GEOLOGY OF MAINE.

BY C. H. HITCHCOCK.

Inasmuch as this report is to be circulated chiefly among those who have never found time to devote much attention to scientific study, it has been thought by some that the elements of geology should constitute its chief portion. But little need be written preliminary to the account of our explorations the past season, because a general knowledge of geology is already possessed by intelligent men; and especially because four reports upon the Geology of Maine, made twenty years ago by Dr. C. T. Jackson, have already been distributed throughout the State. We will notice therefore only such fundamental features of the science as have an intimate connection with the details of the report.

Stratified and Unstratified Rocks.

Geologists consider it settled that the earth was formerly a mass of molten matter similar to lava, assuming its present shape of a flattened sphere while its materials were thus plastic. As the medium in which the earth revolves is intensely cold, (at least 75 degrees below zero,) the tendency of the heated mass must have been constantly to throw off heat, and this at length to form a crust upon the surface of the spheroid. As soon as the crust became sufficiently thick for water to accumulate upon it, the process of denudation commenced, wearing away the higher parts of the envelop and depositing the detritus in the lower portions of the surface, or the valleys. At present the radiation of heat from the interior melted mass cannot be great, as the crust must be more than a hundred miles thick.

The original mass of the earth and all igneous rocks are said to