What is the difference between a butterfly and a moth, and how am I to distinguish between them? is a question very often put to the student of insect life—the entomologist.

Butterflies and moths both belong to the Natural Order, Lepidoptera, or scale-winged insects. Butterflies may be distinguished as day flyers, and the moths fly by night. The main physical difference between them appears in the forms of the antennÆ, or horns; in the butterflies these organs are club-shaped at the extreme ends. But the antennÆ of the various species do not all follow a common pattern. In some the knob is abrupt and much smaller, after the manner of a drum-stick; in others, the thickening commences well down the shaft, and is gradually increased until it very much resembles an Indian club. The antennÆ of the moths, on the other hand, show much diversity of form, and in a great many species they are totally different in the male and female. A very common and beautiful form is the feathered, or comblike, antenna; another is long and threadlike, and some show a combination of these two forms; others, again, seem to be striving after the butterfly type, and approach the club shape. It should be noted that not a few moths fly during the day, but it is rare, exceedingly rare, to find a butterfly abroad after sundown. With a little practice in observation, the novice soon learns to distinguish between the two.

The stages of development of butterflies and moths are practically the same: first the egg; next the caterpillar, or larva; then the pupa, or chrysalis; and, lastly, the imago, or perfect insect.

The eggs of the Lepidoptera are surpassingly beautiful. Are they like birds’ eggs? Not at all! In the first place they are too minute for comparison with the larger product of the birds; both in colour and form they more nearly resemble small shells or pearls, as a great many of them are beautifully opalescent, especially when empty. A good hand-lens will reveal a great deal of their beauty, but the low power of an ordinary compound microscope will be necessary to enable you to see all the nice detail of pattern sculptured on their surfaces. Each species of butterfly, or moth, produces eggs of particular shape and ornamentation, so it is quite possible, in most cases, to say to which species an egg belongs. How long the egg may remain unhatched depends a good deal upon which butterfly’s egg it is, the season of the year, and the temperature. Not many butterflies pass the winter in this country in the egg state, that season being usually passed either as a half-fed hibernating caterpillar, or as a chrysalis; and in a few cases it is only the female which passes the winter in some secure retreat, to emerge again in the spring, and then deposit her eggs on the fresh-growing verdure. But, generally speaking, eggs laid during the summer hatch out in from ten to sixteen days. And it is well to be on the lookout for the young larvÆ even earlier, if you intend to rear some species in confinement. If you have secured eggs to rear from, watch them from day to day to see if they darken, as they often assume a dark leaden hue immediately before hatching. This is a useful warning, and serves as a hint to have plenty of fresh food ready for the young family about to arrive.

The caterpillars are ravenous eaters; you will not notice this fact particularly at first, because they are then such tiny creatures, but in proportion to their size their eating capacity is enormous. They grow at an exceedingly rapid rate and to such an extent that they literally burst their skins! In a very short time—three or four days—the old skin bursts and out comes Mr. Caterpillar with a brand-new one. And this is the manner of their growth; several times (five or six) this skin-shedding process is repeated. And then the creature prepares for the last and final change before turning into a butterfly.

There are one or two more points I would ask you to notice about our caterpillar ere we pass on to consider his next stage. The legs are generally sixteen in number. There are six true legs, one pair on each of the first three body-segments behind the head; four more pairs near the anal end, and the last segment carries another pair, known as the “anal claspers.” The first six may be said to represent the same legs in the perfect insect. Note also the breathing holes, or spiracles, placed in a row along either side of the larva. The head seems to carry very large eyes, but it does not really do so; the real eyes are very minute, and it requires a good strong pocket-lens to make them out. There are twelve of them all told, and they are not all of equal size. There are six on either side of the mouth, and the three larger ones on each side are not very difficult to find. The mouth is furnished with strong mandibles for biting and chewing food, and also contains the spinneret for the production of the silk used on various occasions. All these details should be carefully noted—the head, the eyes, the breathing spiracles, the mandibles, the fore-legs and claws, and the hind- or pro-legs. Mark the totally different types of feet which terminate these two sets of legs. You will need to use your lens for this observation, and to enable you to see the beautiful structure of the pro-leg foot, it will be necessary for you to examine it through a compound microscope. It is well for the young entomologist to know these more prominent features of a caterpillar’s economy, if for no other reason than to be able to answer the questions that are sure to be put to him on these and many other points.

But only a small percentage of the larvÆ that are born into the world live to become butterflies; some seasons a larger number than usual may escape, and then we have a butterfly year, but the relentless ichneumon flies soon restore the balance. They, too, have their young to provide for, and a strange mode of existence they have. Once you get to know these ichneumons at sight, you will be astonished at the number of them. All the summer through you will find them hawking about the trees, bushes, nettles, and heather, and, indeed, wherever larvÆ are to be found, there, too, you will find these flies. There are many species of them. Once a female has discovered a larva its doom is sealed. The ordinary larva has very few defensive weapons; he may wriggle and squirm and look terrifying, but all the same the ichneumon sets about her task of placing one or two, and in many cases a dozen or two, of her eggs either upon or under his skin. These eggs soon hatch, and the little white maggots pass their existence inside the doomed creature, eating all the tissues away, at first avoiding the vital organs, which they leave until the last. When they have reached their allotted span, and are about to change to the pupa state themselves, they soon finish off their victim, and all that remains of what might have been a brilliant butterfly is a little shrivelled bit of skin and a host of little—or it may be a few big—black, brown, or grey flies. Sentiment apart, these parasitic flies are extremely useful. When you consider the large number of eggs laid by a single female butterfly or moth—from two to six hundred is a fair average—you will realize that if this enormous progeny were to survive and go on increasing without any check, the vegetation of the world would very soon prove quite inadequate to support the vast army of caterpillars, to say nothing of you and me.

You may at some time find a dozen or two larvÆ of some particular species of butterfly or moth, and at the time of collecting them they may seem healthy and all right, but weeks afterwards you may discover that only a very small number will change to chrysalids, the ichneumons having had the rest. If you can catch and induce a female butterfly to give you a batch of eggs in captivity, then you may be sure, providing your treatment of them has been right, that all your brood will arrive at the perfect state.

The next stage we have to consider we will pass over briefly. The change from the larva to the chrysalis is always a very fascinating performance to watch, not that one could sit and see the whole performance right through from start to finish, the time occupied is too long for that. Generally the process lasts a day or two, but by watching at frequent intervals, where several individuals are engaged at the same operation and each at its own stage of the work, it is not difficult to follow the whole process of the transformation. Try it with the larva of the Large Garden White butterfly, perhaps the commonest, and therefore the easiest to procure; you will gather plenty of “stung” or “ichneumoned” examples, but still a sufficient number should be clean to serve your purpose.

We will not enter into all the details of the “spinning-up” process and describe how an attachment is secured at the anal extremity, and how our little friend “loops the loop.” Some species, such as the Tortoiseshell, get over this part of their difficulty by omitting the loop altogether, and therefore hang head downward, suspended only by the hooks and silk at the tail. Concealment during this stage is the creature’s only hope and chance of survival; other defence they have none. Their colour may occasionally protect them by virtue of making them harmonize beautifully with their surroundings. The ichneumons seldom molest them during the chrysalis stage; but birds and small animals have sharp eyes when foraging for food, so it is usually far more difficult to discover these chrysalids than to find the feeding caterpillars.

The time passed as a chrysalis is very variable; ten days to a fortnight in summer is sufficient for many species; others pass over the whole winter, like the spring brood of our common white butterflies, so that these can be sought for during the winter months under the overhanging portion of palings, walls, outhouses, and in similar situations. The cold does not seem to injure them; it may, and generally does, retard their emergence, and possibly has some effect on the colours of the wings, but it cannot change their ultimate pattern. Experiments have been tried with various chrysalids, part of a brood being hatched out after being submitted to a very low temperature, and another part of the same brood after being treated with a high temperature. Speaking generally, the coloration of those subjected to the cold treatment was brightened and intensified, and Nature does the same thing in her own way. The early summer butterflies, which pass through the winter as chrysalids, are almost invariably larger and brighter than the midsummer or autumn brood of the same species.

But suppose our caterpillar to have successfully run the gauntlet—ichneumon, bird, beast, and beetle—and to have become a healthy pupa, and that the time has arrived when he must make the last and greatest transformation in his short and interesting career. Several days prior to his exit as a butterfly taking place, a noticeable change occurs in the apparent colour of the chrysalis.

As a matter of fact it is not the chrysalis shell which is changing colour, but the developing insect, the colours of which are beginning to show through it, at first rather faintly; but latterly the pattern of the wings can be distinctly seen, and the whole body surface gets darker. When this stage is reached, the advent of our butterfly is not long delayed. The hour chosen is usually early in the morning, so that by the time the sun is high and the fresh perfumed flowers are nodding in the breeze, our little butterfly has expanded and dried his wings, and is now quite prepared for the beautiful and consummating act in the wonderful drama of his existence.

PLATE 2.
Method of Setting with Bristle and Braces

While he is drying his wings and preparing for a life amongst sunshine and flowers, we might spend a few minutes with him ere he leaves us, and the more so, as now he looks his very best, arrayed in all his new-found finery. Such wings! no wonder he looks proud as he slowly opens and closes them, repeating this action over and over again as if to prove their smooth working before he launches forth upon the air.

And the wonderful pattern of these wings is all built up of tiny scales placed as regularly as the slates on a roof. Your pocket-lens will show you much of this, but to examine the individual scales, their various shapes and structure, you will require a compound microscope. These scales are the “dust” you will find on your finger and thumb if ever you pick up a butterfly in such an unscientific manner. You will notice, too, that the under sides of the wings bear quite a different design from the upper sides; this is nearly always the case, and in many foreign butterflies this difference between the two sides is so very remarkable as to be quite startling in its effect. Well I remember an old sergeant-major, who had spent many years in India, and had done a lot of “butterfly dodging” in his day, telling me of this wonderful effect. He said one would come upon an open piece of meadow-land blazing with flowers and butterflies, but, on being disturbed, the whole crowd of insects would rise in the air, and then, he would say, they looked like a different set altogether. When you capture a few specimens of any species, examine closely the under sides, and in any case, if you wish to preserve them, always set one of each sex with the under side uppermost.

Next to the wings the head claims our attention; it supports three very essential organs—the eyes, the horns, or antennÆ, and the tongue, or sucker.

The antennÆ are undoubtedly the organs of smell, which is perhaps the most highly developed sense in the Insect World. That the eyes are a marvel of beauty, and that the tongue is a finely finished little instrument for its work no one can question; but the sense of smell has a much longer range than even the eye, with all its facets. And you will generally find, in relation to the faculty which any animal or insect has to exert most so as to procure its food and propagate its kind, the organ of that faculty reaches the highest point of development and service.

The eyes of the condor and the gannet must be marvellous in range and penetrating power. I have watched scores of the latter birds sailing and hovering 150 feet and more above a troubled sea. Suddenly there would be a slight pause, and then a rocket-like dive right down into the waves below. To see a fish on the surface from such a height would be a great feat, but to see and catch one a dozen feet deep in a broken sea as a gannet can do, is wonderful indeed.

With butterfly and moth the sense of smell is of the greatest importance. Their vision is good, but short in range; so to find the flowers wherein lies their food the sight is good, but the power to detect them by scent must be far better. “Over the hedge is a garden fair,” and if a butterfly cannot see through the hedge, he can at least smell through it. He could fly over it? Yes, but if his sense of smell says there is nothing there for him, you see he is saved the time and trouble; and his life is short.

“Assembling” and “treacling” for moths are two methods employed by insect-hunters to secure an abundance of specimens otherwise difficult to obtain, and in both cases it is this same wonderful sense of smell which is the insect’s undoing.

For “assembling,” a captive virgin female is taken at dusk to the locality where the species is likely to occur, and if males are about they very soon make their appearance. The female being in a gauze-covered box, they will swarm over it in their efforts to find an entrance, and when thus engaged can be easily captured. As for the subtle odour emitted by the lady, you or I could never detect it, yet these moths come swarming from far and near. I once witnessed a curious phase of this instinct on a hillside in Arran. My attention was arrested by a number of males of Bombyx Quercus (variety, CallunÆ), keeping near and flying over a certain spot, and, thinking a female might be about, I went over to investigate. It was a female, but a dead and crushed one; how it had met its end I could only conjecture; but evidently, although the insect was mutilated, the scent still lingered, and brought the males circling round. This large moth flies boldly during the day, and in Arran the larvÆ feed on the heather.

The eyes of a butterfly are large and of the usual insect pattern—i.e., compound, being made up of a number of tiny lenses, hexagonal in shape, like the honeycomb of the domestic bee. Roughly, about three thousand of these lenses go to make up the two eyes. As pointed out, their range of vision is comparatively short, but within their range vision must be very keen—before, behind, above, and below. I once saw a sparrow try to capture a Large Garden White in a street in the town; he darted at it again and again, much in the manner of the ordinary spotted flycatcher, but the butterfly seemed to have no difficulty in evading him, and eventually he gave up the game.

A small portion of the eye makes a good slide for the microscope, but the individual lenses are hardly visible through an ordinary hand-glass. On the top of the head are one or two small simple eyes, which do not look as if they could be of much service, but one never knows, and the butterflies will not tell, although they have long tongues.

The tongue is a very pretty structure; when not in use it lies coiled up in spiral fashion like a watch-spring, and is then well protected by two little side-covers called the “palpi.” Needless to say, the tongue cannot sting. No moth or butterfly has a stinging organ; the tongue is too delicate for any “cut and thrust” work. It is not difficult to mount a butterfly’s tongue for the microscope, and its examination well repays the trouble. Particularly noticeable under the microscope are the little bell-shaped suckers placed in long rows near the tip. If you wish to make and examine a cross section, take the head of a freshly killed specimen and extend the tongue in a little melted paraffin wax; when this is thoroughly set, cut it across in very thin slices with a sharp razor; place one on a glass slide, then on to the microscope stage, and there you are! You will soon discover that the simple-looking tube is a very complicated affair, and quite a little study in itself.

We will not linger over what remains of the anatomy of our butterfly. The legs are six in number, but occasionally the first pair are useless for walking, and only the middle and last pairs are fully developed. Always remember the maximum number of legs for all insects is six. Caterpillars may have more or less; they occur as footless grubs with no legs at all, while some have as many as sixteen legs.

The last, or abdominal, section of a butterfly’s body carries the sexual organs; it is usually more slender in the males than in the females.