Insect Stories

by Vernon L. Kellogg

[HOUSES OF OAK]

There are eight different kinds of oak-trees growing on or near the campus where Mary and I live. And each kind of oak-tree has several kinds of houses peculiar and special to it. Which makes altogether a great many styles and sizes of houses of oak for Mary and me to get acquainted with. For we have made up our minds to know them all, and something about the creatures that live in them. This is a large undertaking, we are finding, but an intensely interesting and delightful one. Some of it is quite scientific, too, which makes us proud and serious. We are keeping notes, as we did about Argiope and the way it handled flies and bees, and some day we shall print these notes in the proceedings of a learned society, and make a real sensation in the scientific world. Anyway we think we shall. Just now, however, we shall only tell the very simplest things about these houses of oak and their inhabitants, for we suppose you wouldn't be interested in the harder things; perhaps, indeed, not even understand them all.

Although, as I have already said, there are eight different kinds of oak-trees growing in our valley and mountains, two of these kinds, the live-oaks and the white oaks, are by far the most common and numerous. As one stands upon the mountain tops or foothills and looks down and over the broad valley, all still and drowsy under the warm afternoon sun, it seems as if you were looking at a single great orchard with the trees in it in close-set regular lines and plots in some places, and irregularly scattered and farther apart in other places. Where they are regular and close together, they really are orchard trees; where they are irregular and widely spaced and larger, they are the beautiful live-oaks and white oaks that grow in all the grain-fields and meadows and pastures of our valley. The live-oaks have small leaves, dark green and close together, and the head of the tree is dense and like a great ball; the white oaks have larger, less thickly set leaves of lighter green, and the branches are more irregular and straying and they often send down delicate pendent lines that swing and dance in the wind like long tassels. The live-oaks have leaves on all the year through; the white oaks lose theirs in November.

In both of these kinds of trees the oak houses can be found, but especially in the white oaks. And there are, as I have said, many kinds of the houses. Mary and I have found little round ones, big bean-shaped ones, little star-shaped ones, slender cornucopia-like ones, green, whitish, red-striped, pink-spotted, smooth, hairy, rough-coated, spiny ones, and still other kinds. Some of the houses are on the leaves, some on the leaf-stems, some on the little twigs, and some on the branches. Some of the houses stay in the trees all through the year, but most of them drop off in the autumn, especially in the white-oak trees, just as the leaves do.

We go out and hunt for the houses in the trees and among the fallen leaves on the ground under the trees. They are sometimes, especially the little ones, hard to find, for their colors and shapes often seem to fit in with their surroundings, so as to make them very hard to see. But others, like the big ball-shaped white ones shown in Sekko Shimada's picture, are, on the contrary, very conspicuous. If the houses are on the ground, or even if they are still on the tree and we think they are all through being made—and there are various ways of knowing about this, but the most important is the time of year—Mary and I bring them home with us and put them in little bags of fine cloth netting, tarlatan usually, the houses that are alike and from one place being put together in a single bag. Then we tie a string around the mouth of the bag and wait for the dwellers in the houses to come out.

For one has to be careful about trying to see the oak-house dwellers before they are ready to come out. It is much better to await their own sweet pleasure in this matter, than to go digging or prying in, for the houses have no doors or windows until just at the time the dwellers come out! In fact they make the doors as they come out. You will see, after we tell you a little more, that this arrangement is a very good one. Even as it is, various unwelcome intruders find their way into the house much to the annoyance and even to the fatal disaster of the inmates.

So we wait until the dwellers are ready to come out. Or if occasionally we really think we ought to see how things are going on inside, we chop a house or two open and see what we can see. What this is, usually, is a house's insides very unusual and curious, for the rooms occupy so little space and the walls so much. Sometimes there is only one room and that right in the middle, all the rest of the house being just a dense or sometimes loose and spongy wall all around it. In the single room, or in each of the several rooms, we find a curled-up little shining white grub without legs, and of course without wings, and with a head that doesn't seem much like a head, for it has no eyes nor feelers, and most of the time is drawn back into the body of the grub so that it is hardly visible at all. But there is a mouth on this silly sort of head, and the grub eats. What it eats is part of its own house!

The houses, or galls, as the entomologists call them, are of course not actually made by the insects that live in them; they are made by the oak-tree on which they are. But they are only made at the demand, so to speak, of the insects. That is, the oak-galls are formed only where a gall-insect has pricked a live leaf or stem or twig with her sharp, sting-like little egg-layer, and has left an egg in the plant-tissue. Nor does the gall begin to form even yet. It begins only after the young gall-insect is hatched from the egg, or at least begins to develop inside the egg. Then the gall grows rapidly. The tree sends an extra supply of sap to this spot, and the plant-cells multiply, and the house begins to form around the little white grub. Now this house or gall not only encloses and protects the insect, but it provides it with food in the form of plant-sap and a special mass or layer of soft nutritious plant-tissue lying right around the grub. So the gall-insect not only lives in the house, but eats it!