The natural History of the Swallow-tail’d Butterfly, and its Ichneumon.
IN a former Number of this work, our fair readers may remember we gave them some account of the several metamorphoses or alterations from one state to another, which various classes of animals undergo. But although we mentioned in general terms the changes of the butterfly kind, yet as we entered into no very particular detail in regard to them, it will not, we hope, be look’d on as any kind of repetition, if we take up a short portion of their time on that head here.
That beautiful and almost infinitely varied genus of insects, which is so well known by the names of butterfly and moth, (the one meaning only a day, the other a night fly,) is to be ranked with those of the most perfect change, as every one of this kind passes through the greatest number of states that has yet been discovered amongst animals, viz. the egg, worm, chrysalis, and fly. But to render these terms more clear, and at the same time to relate the general history of this extensive province in the great kingdom of nature, we shall illustrate it with an example.
The butterfly we have fixed on for this purpose is one of the most beautiful as well as the largest that we know of English growth: it is commonly known by the name of the Swallow Tail, from the figure of its under-wings, which terminate in some measure like the tail of that bird. Some authors indeed have called it the fennel fly, because the caterpillar which produces it, is fondest of feeding on fennel, though it is not uncommonly found upon dill, parsley, carrot, and several other umbelliferous plants. But Linnaeus, whose names are frequently as absurdly arbitrary, as his system is laboriously ingenious, has bestowed on it the name of Machaon, who was a celebrated Greek physician, and son to Esculapius.
His first state is, like that of all other insects, an egg, which is laid by its parent on the plant that is afterwards to become food for the infant worm at the emersion into life. She, however, seldom lays more than two, never more than three or four on one plant, and those singly and at a considerable distance from each other. These eggs are yellow and of a conical form, and are so sixt by the female, with a strong glutinous matter, to the stalk of the plant, as to stand all the fiercest attacks of the wind and rain, without being forced from their hold. One of them, as affixed to a piece of a stalk is represented at c, in the annexed plate.
These eggs, which are generally laid in June, July, or August, come to perfection in about a month’s time; when the young caterpillar breaks forth the same in every respect but bulk that it appears when full grown: its body is green, annulated, or striped transversely with striae of black, each ringlet studded with spots of a bright scarlet. This caterpillar leads a very solitary life, there seldom being more than two to be found on one plant. The reason of this may probably be, that the umbelliferous plants in general, and more particularly the fennel, which, as we have before observed, is the favourite food of this caterpillar, afford but a very small quantity of foliage; and that this worm before its next change, grows to a very considerable bulk. The parent, instructed by that most infallible of all properties, instinct, purposely deposits her eggs so sparingly, lest the future offspring forming too large a colony to be maintained by one plant, should be forced to seek out for fresh quarters, in which case, unless they chanced to meet with another plant of the same kind with that they quitted, they must inevitably perish. They are very slow in feeding, and in their growth cast their skins several times before they change into a Chrysalis. In some the green is more or less bright, but in general the colours are more vivid in their infant state than when more fully grown.
This caterpillar has one property peculiar to itself, which is, that on the approach of any fly or ichneumon, it puts forth from the two red spots on its forehead, a pair of antennae, or horns like those of a snail, and then beats about from side to side with the fore part of its body, in order to prevent the Ichneumon from emitting or fixing any eggs on its body. Two of these caterpillars at their full growth, the one at rest, the other with its antennae put forth and defending itself from the ichneumon, are represented at d and e.
His next state is that of the Chrysalis, which, foreseeing for some little time beforehand, he prepares for, by abstaining from food, and discharging his excrements; which done, he fixes himself by his two hind legs, with a web, to some part of the stalk of the plant, and then spinning a thin single thread across his body, between the third and fourth joint, remains as it were suspended and immoveable for about four and twenty hours, when by a continued motion the skin is stripped off, and he becomes converted to the Chrysalis, shewn at f.
This transformation happens in August or September, according as the spring may be early or late; and in this situation he passes the whole winter and ensuing spring, coming out about the May or June following, in the form of the large and beautiful butterfly, represented at A and B. The wings are of a bright yellow, with borders and bands of a deep black; the under pair still farther decorated with a chain of fine blue spots, and two circles of a full orange. These flies feed on the dulcet juices of flowers, the moisture of which they suck in by means of a long proboscis, wherewith they are provided. They are frequenly seen sitting with their wings folded, as at a, on the ground, near rivers and ponds.
Those who are desirous of breeding these flies themselves, in order to see their changes, or to procure the butterfly in greater perfection, may find the caterpillars, during the months abovementioned, in places abounding with the umbelliferous plants. When discovered, they must be carefully supplied with fresh food: when the Chrysalis is obtained, it must be kept temperate, and not much disturbed: and the box or cage must be roomy, in order for the wings to expand themselves, otherwise they will be liable to be injur’d, when the fly issues from the shell.
They copulate as soon as they appear in the fly state, lay their eggs in about a fortnight afterwards, and then soon die.
As in our description of the abovementioned butterfly we took notice of the manner in which the caterpillar whereby it is produced, defends itself from the attacks of the Ichneumon, it may not be improper in this place to explain what we mean by that term; especially as it opens an entire new scene in the natural history of the insect tribe, in which the great parent who provides sustenance for all creatures in different ways, and has in general contrived it so, that the larger and more powerful shall prey on and destroy the smaller ones, seems to contradict herself, by enabling a small animal to subsist on the very flesh and juices of one much larger than itself; and that even whilst it continues alive, and apparently in good health.
The Ichneumon then is a class of small flies, whereof there are a very great variety of species; the proper nourishment of the worm of which is, the body of some other caterpillar. On this account the parent finds means to deposit its eggs on, or rather underneath the skin of such caterpillar, which hatching in due time, the worm immediately begins to feed on the very entrails of the caterpillar; nor ever quits it, even though it frequently changes into a Chrysalis, as if it were by a metamorphosis to elude its enemy, till the time when his own change is to happen, which he undergoes first into an Aurelia, and then into a Fly, emerging in the last form from the very spot where he first found residence in that of an egg.
The fly which is represented in the same plate with the Swallow Tail, sitting at g, and in its flying position at b, is one of this sort; preys on the caterpillar of that butterfly, and is produced in the following manner.
The female fly emits an egg, (which is represented in its natural size and shape i,) on the caterpillar, either at the time when the caterpillar is asleep, or soon after it has received a new skin. This egg, by means of a glutinous matter, which the parent emits at the same time with it, is so fixed where it is deposited, as not to be got off without the utmost difficulty; and being in less than seven days hatched by the warmth of the caterpillar’s body, and the heat of the sun, the animal produced from it eats its way thereinto, on that part, whereby it adheres to the body. The empty shell covering the entrance or incision made by the newly hatched maggot, the wound becomes quickly healed, and the worm feeds on the entrails of the caterpillar till such time as he comes to his maturity, which not being in less than eighteen or twenty days, it frequently happens that the caterpillar becomes in the mean while transformed into a Chrysalis. The maggot, however, contained either within the caterpillar or chrysalis when grown to its full bulk, will eat its way through and fall to the ground; at which time it is in size and shape as represented at k, and of a dusky white; but in less than two hours is formed into a Chrysalis, as at l, in which state, if this change happens in summer, it continues for only about three weeks; but if late in autumn, as is sometimes the case, it remains during the whole winter in that state, and the fly, by eating its way through the shell, comes forth in the spring following.
N. B. All Caterpillars or Chrysales impregnated by Ichneumons, become spoiled, and do not produce any butterfly or moth. There are great varieties of the Ichneumon fly; but the one we have here described is of the kind called by Linnaeus Larvaxum.
Description of the copper plate contained in our last Number.
Figure 1. The Calamary compleat, with all its arms extended. Figure 2. and 3. Two of the suckers belonging to the long arms of the Calamary, detached and represented in different views.
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