« PreviousContinue »
honey-yellow color; hind wings with a short rounded tail on the hind angles, and a broad silvery band across the middle of the under side. Expands from 2 to 24 inches.
This large and beautiful insect makes its appearance, from the middle of June till after the beginning of July, upon sweetscented flowers, which it visits during the middle of the day. Its flight is vigorous and rapid, and its strength is so great that it cannot be captured without danger of its being greatly defaced in its struggles to escape. The females lay their eggs, singly, on the leaves of the common locust-tree (Robinia pseudacacia), and on those of the viscid locust (Robinia viscosa), which is much cultivated here as an ornamental tree. The caterpillars are hatched in July, and when quite small conceal themselves under a fold of the edge of a leaf, which is bent over their bodies and secured by means of silken threads. When they become larger they attach two or more leaves together, so as to form a kind of cocoon or leafy case to shelter them from the weather, and to screen them from the prying eyes of birds. The full-grown caterpillar, which attains to the length of about two inches, is of a pale green color, transversely streaked with darker green, with a red neck, a very large head roughened with minute tubercles, slightly indented or furrowed above, and of a dull red color, with a large yellow spot on each side of the mouth. Although there may be and often are many of these caterpillars on the same tree and branch, yet they all live separately within their own cases. One end of the leafy case is left open, and from this the insect comes forth to feed. They eat only, or mostly, in the night, and keep themselves closely concealed by day. These caterpillars are very cleanly in their habits, and make no dirt in their habitations, but throw it out with a sudden jerk, so that it shall fall at a considerable distance. They frequently transform to chrysalids within the same leaves which have served them for a habitation, but more often quit the trees and construct in some secure place a cocoon of leaves or fragments of stubble, the interior of which is lined with a loose web of silk. They remain in their cocoons without further change throughout the winter, and are transformed to butterflies in the following summer. The viscid locust-tree is sometimes almost completely stripped of its leaves by these insects, or presents only here and there the brown and withered remains of foliage, which has served as a temporary shelter to the caterpillars.
II. HAWK-MOTHS. (Sphinges.") Linnæus was led to give the name of Sphinx to the insects in his second group of the Lepidoptera, from a fancied resemblance that some of their caterpillars, when at rest, have to the Sphinx of the Egyptians. The attitude of these caterpillars is indeed very remarkable. Supporting themselves by their four or six hind legs, they elevate the fore part of the body, and remain immovably fixed in this posture for hours together. In the winged state, the true Sphinges are known by the name of humming-bird moths, from the sound which they make in flying, and hawk-moths, from their habit of hovering in the air while taking their food. These humming-bird or hawkmoths may be seen during the morning and evening twilight, flying with great swiftness from flower to flower. Their wings are long, narrow, and pointed, and are moved by powerful muscles, to accommodate which their bodies are very thick and robust. Their tongues, when uncoiled, are, for the most part, excessively long, and with them they extract the honey from the blossoms of the honey-suckle and other tubular flowers, while on the wing. Other Sphinges fly during the daytime only, and in the brightest sunshine. Then it is that our large clear-winged Sesiæ make their appearance among the flowers, and regale themselves with their sweets. The fragrant Phlox is their especial favorite. From their size and form and fan-like tails, from their brilliant colors, and the manner in which they take their food, poised upon rapidly vibrating wings above the blossoms, they might readily be mistaken for humming-birds. The Ægerians are also diurnal in their habits. Their flight is swift, but not prolonged, and they usually alight while feeding. In form and color they so much resemble bees and wasps as hardly to be distinguished from them. The
See page 229.
Smerinthi are heavy and sluggish in their motions. They fly only during the night, and apparently, in the winged state, take no food; for their tongues are very short, and indeed almost invisible. The Glaucopidians, or Sphinges with feathered antennæ, fly mostly by day, and alight to take their food, like many moths, which some of them resemble in form, and in their transformations. The caterpillars of the Sphinges have sixteen legs, placed in pairs beneath the first, second, third, sixth, seventh, eighth, ninth, and last segments of the body; all of them, except the Ægerians and Glaucopidians, have either a kind of horn or a tubercle on the top of the last segment, and, when at rest, sit with the fore part of the body elevated.
Having devoted a large portion of this treatise to a description of the spinning moths, my observations on the other insects of this order must be brief, and confined to a few species, which are more particularly obnoxious on account of their devastations in the caterpillar state. Those persons who are curious to know more about the Sphinges than can be included in this essay, are referred to my descriptive catalogue of these insects, contained in the thirty-sixth volume of Professor Silliman's Journal of Science."
Every farmer's boy knows the potato-worm, as it is commonly called; a large green caterpillar, with a kind of thorn upon the tail, and oblique whitish stripes on the sides of the body. This insect, which devours the leaves of the potato, often to the great injury of the plant, grows to the thickness of the fore-finger, and the length of three inches or more. It attains its full size from the middle of August to the first of September, then crawls down the stem of the plant and buries itself in the ground. Here, in a few days, it throws off its caterpillar-skin, and becomes a chrysalis, of a bright brown color, with a long and slender tongue-case, bent over from the head, so as to touch the breast only at the end, and somewhat resembling the handle of a pitcher. It remains in the ground through the winter, below the reach of frost, and in the following summer the chrysalis-skin bursts open, a large moth crawls out of it, comes to the surface of the ground, and
mounting upon some neighboring plant, waits till the approach of evening invites it to expand its untried wings and fly in search of food. This large insect has generally been confounded with the Carolina Sphinx ( Sphinx Carolina of Linnæus), which it closely resembles. It measures across the wings about five inches; is of a gray color, variegated with blackish lines and bands; and on each side of the body there are five round, orange-colored spots encircled with black. Hence it is called by English Entomologists Sphinx quinquemaculatus, the five-spotted Sphinx. Its tongue can be unrolled to the length of five or six inches, but, when not in use, is coiled like a watch-spring, and is almost entirely concealed, between two large and thick feelers, under the head.
Among the numerous insects that infest our noble elms the largest is a kind of Sphinx, which, from the four short horns on the fore part of the back, I have named Ceratomia* quadricornis, or four-horned Ceratomia. On some trees these Sphinges exist in great numbers, and their ravages then become very obvious; while a few, though capable of doing considerable injury, may escape notice among the thick foliage which constitutes their food, or will only be betrayed by the copious and regularly formed pellets of excrement beneath the trees. They are very abundant during the months of July and August on the large elms which surround the northern and eastern sides of the common in Boston; and towards the end of August, when they descend from the trees for the purpose of going into the ground, they may often be seen crawling in the mall in considerable numbers. These caterpillars, at this period of their existence, are about three inches and a half in length, are of a pale green color, with seven oblique white lines on each side of the body, and a row of little notches, like saw-teeth, on the back. The four short horns on their shoulders are also notched, and like most other Sphinges they have a long and stiff spine on the hinder extremity of the body. They enter the earth to become chrysalids and pass the win
Ceratomia, derived from the Greek, means having horns on the shoulders, a peculiarity which I have not observed in any other Sphinx.
ter, and come forth in the winged state in the month of June following, at which time the moths may often be found on the trunks of trees, or on fences in the vicinity. In this state their wings expand nearly five inches, are of a light brown color, variegated with dark brown and white, and the hinder part of the body is marked with five longitudinal dark brown lines. A young friend of mine, in Boston, once captured on the trunks of the trees a large number of these moths during a morning's walk in the mall, although obliged to be on the alert to escape from the guardians of the common, whose duty it was to prevent the grass from being trodden down. Nearly all of these specimens were females, ready to deposit their eggs,
with which their large bodies were completely filled. On being taken, they made scarcely any efforts to escape, and were safely carried away. It would not be difficult, by such means, very considerably to reduce the number of these destructive insects; in addition to which it might be expedient, during the proper season, for our city authorities to employ persons to gather and kill every morning the caterpillars which may be found in those public walks where they abound.
From the genus Sphinx I have separated another group to which I have given the name of Philampelus,* from the circumstance that the larvæ or caterpillars live upon the grape-vine. When young they have a long and slender tail recurved over the back like that of a dog; but this, after one or two changes of the skin, disappears, and nothing remains of it but a smooth, eye-like, raised spot on the top of the last segment of the body. Some of these caterpillars are pale green and others are brown, and the sides of their body are ornamented by six cream-colored spots, of a broad oval shape, in the species which produces the Satellitia of Linnæus, narrow oval and scalloped, in that which is transformed to the species called Achemon by Drury. They have the power of withdrawing the head and the first three segments of the body within the fourth segment, which gives them a short and blunt appearance when at rest. As they attain to the length of three inches or more, and are thick in
* The literal signification of this word is I love the vine.