Butterflies and Moths Part 1

b.u.t.terflies and Moths.

by William S. Furneaux.

PREFACE

The favourable reception with which the 'Out-door World' has been greeted has encouraged the publishers to issue a series of volumes dealing in fuller detail with the various branches of Natural History treated of in that work. Necessarily each subject was only briefly touched upon, but the study is of so enticing a character that 'appet.i.te grows by feeding,' and the students of the 'Out-door World,' having tasted the sweetness of companionship with Nature, will not rest satisfied with the help afforded by that handbook. Each one will want to go deeper into that particular department which most appeals to his own inclinations.

The present volume is written expressly for those who desire to extend their knowledge of the British Lepidoptera, or, to use the more popular names, 'b.u.t.terflies and Moths.'

The general characteristics of this interesting order of insects are described somewhat fully, but, of course, it would be impossible to give an individual account of all the British Lepidoptera in a work of this size, so a selection has been made such as will satisfy the requirements of the great majority of those who intend to take up this particular branch of entomology. The number of British b.u.t.terflies, however, is so limited that a place has been found for a figure and a description of every species; and, of the larger moths, many of the common and typical kinds have been included. An introduction to the study of the Micro-lepidoptera has also been added.

No trouble has been spared to render this work thoroughly practical. In addition to the verbal descriptions of so many species, twelve coloured plates and a large number of woodcuts have been specially prepared to help the student in his work. It is believed that the extreme care with which these have been produced will render them of the greatest a.s.sistance to the collector in the recognition of his specimens.

But he has not only to recognise his specimens--he must first catch them; and here full directions have been given to insure success in this part of his work, as well as in the management, preservation, and arrangement of his captures.

The Author hopes that this volume may be the means of adding many happy hours--hours of the purest enjoyment--to the lives of those whom he has succeeded in luring into the fields and lanes and woods of the Out-door World.

PART I

STRUCTURE AND LIFE-HISTORY OF THE LEPIDOPTERA

CHAPTER I

_GENERAL CHARACTERS_

The word _Lepidoptera_, which you see at the head of this page, is the name of the order of insects to which this volume is to be devoted. It is formed from two Greek words, one (_lepis_) signifying a _scale_, and the other (_pteron_) denoting a _wing_; and was applied by the great naturalist Linnaeus to the scaly-winged insects popularly known as b.u.t.terflies and Moths.

[Ill.u.s.tration: FIG. 1.--SCALES FROM THE WINGS OF b.u.t.tERFLIES.]

Every one of my readers has undoubtedly handled some of the interesting creatures of this group--having been led to do so either by the extreme beauty of their clothing, or, perhaps, from a murderous intent in order to protect his own garments from the ravages of a supposed marauder. A light mealy powder will probably have been observed afterwards on the fingers that have touched the victim's wings.

This powder, although it sometimes presents a beautiful glossy surface when spread over the skin, does not exhibit any definite form or structure without a more minute examination. Yet these are the scales that led the immortal naturalist to invent the somewhat long but useful term _Lepidoptera_.

The very next time the opportunity offers itself, dust off a little of the mealy powder with a small and very soft brush on to a strip of white paper or a slip of gla.s.s, and examine it with a powerful lens or the low power of a compound microscope. What a sight you will then behold! Each little particle of dust is a beautifully formed scale, stamped with a number of minute rounded projections, and often displaying the most gorgeous colours. A great variety of designs and tints are often exhibited by the 'dust' from a single wing. Take, for instance, for your inspection, scales from the wing of one of our commonest insects, the Small Tortoisesh.e.l.l b.u.t.terfly (Plate III), and you will be surprised at the pleasing contrasts. But when your curiosity leads you to deal with others in the same manner, the varied display of forms and colours is simply amazing.

[Ill.u.s.tration: FIG. 2.--PORTION OF THE WING OF A b.u.t.tERFLY FROM WHICH SOME OF THE SCALES HAVE BEEN REMOVED.]

In order that we may learn still more of the structure of the wings of the _Lepidoptera_, we will examine a portion of one from which some of the scales have been removed, again bringing the lens or the microscope into our service. We now see that the scales are arranged in rows with great regularity on a thin and transparent membrane, which is supported by a system of branching rays. And the membrane itself, in parts which have been laid bare, is marked with regular rows of dots--the points at which the scales were originally attached by means of short hollow rods.

The framework that supports the thin membrane we have spoken of as consisting of a system of _rays_, but to these the terms _veins_, _nerves_, _nervures_, or _nervules_ are more commonly applied by various naturalists. We cannot do better, however, than adhere to the name originally used, for the structures in question do not perform the functions of veins, though at first they contain blood, nor are they themselves parts of the nervous systems of the insects to which they belong.

The result of our examination of the wings of b.u.t.terflies and moths has been to justify the application of the term _Lepidoptera_; but we must now study other equally important and interesting features of the structure of these insects. First, let us note the general form of the body.

[Ill.u.s.tration: FIG. 3.--BODY OF A b.u.t.tERFLY--UNDER SIDE.

1-7, segments of the abdomen; 8, a.n.a.l extremity; _a_, antennae; _b_, tarsus; _c_, tibia; _d_, femur; _e_, palpi; _f_, head; _g_, thorax.]

A cursory glance at this portion of the creature's anatomy will show that it consists of three distinct and well-defined parts. In front there is the head, the size of which is somewhat small in proportion.

Two very large eyes make up the greater portion of its bulk. It is remarkable, too, that b.u.t.terflies possess eyes proportionately much larger than those of moths. Now, since b.u.t.terflies always fly by day, and moths are, generally speaking, nocturnal insects, we might be led to suppose that the reverse of this arrangement would have suited the creatures better; for a small eye, we should think, would be able to collect sufficient light in the daytime to form a bright image, and a larger light-receiving area would be necessary during the darker hours for the same purpose. But it is evident that the sense of vision must depend on other conditions besides the size of the eye; and as these conditions are not understood in relation to the eyes of insects, any attempt at an explanation would be quite useless.

The eye of a b.u.t.terfly or moth is worthy of a closer examination, for it is a most beautiful and marvellous structure. The outer globular transparent membrane--the _cornea_--is divided into a large number of minute polygonal _facets_, each one of which admits light into a small conical compartment surrounded by a coloured membrane, and supplied with a fibre of the nerve of vision (the _optic_ nerve). Hence the eye is often spoken of as _compound_.

If you look closely into the eyes of various b.u.t.terflies and moths you will generally see a ground colour of grey, blue, brown, or black; but when viewed at certain angles in a strong light the most gorgeous hues of metallic brilliancy--gold, copper, and bronze--are to be observed.

All such colours are due to the reflection of light from the colouring matter that lies between the numerous conical compartments.

[Ill.u.s.tration: FIG. 4.--SECTION OF THE EYE OF AN INSECT.]

A glance at the section of a compound eye will show you that all the little cones radiate from a common centre. And, as each little compartment is surrounded by opaque colouring matter, it is clear that perpendicular rays only are capable of penetrating to its base and exciting the nerve fibre that lies there. Thus each little division of a compound eye forms its own image of the object that happens to be exactly opposite its facet. But how many facets do we find in a single eye? Sometimes only a few hundreds, but sometimes as many as seventeen or eighteen thousand! We must not, however, conclude that the nature of the vision of b.u.t.terflies and moths is necessarily very different from our own. We have two eyes, but the images formed by them are both blended, so that we do not see double. We can understand, therefore, that the thousands of images formed in a single eye may be blended together so as to form one continuous picture. Still there remains this difference: while in our own case the two images formed by the two eyes are practically the same, in the case of insects every one of the little conical tubes of a compound eye forms an image of an object that cannot possibly be formed by any one of the others. Thus, if the lepidopterous insect sees a continuous picture of its surroundings, such a picture is produced by the overlapping and blending, at their edges, of hundreds or thousands of distinct parts.

There is yet another interesting difference between the vision of these insects and that of ourselves. As already stated, our two eyes are both turned toward the same point at the same time. But look at the b.u.t.terfly's eyes. Here are no movable eyeb.a.l.l.s, and the two eyes, placed as they are at the _sides_ of the head, are always turned in _opposite_ directions. The corneae, too, are very convex; and consequently the range of vision is vastly wider than ours. A boy is often easily surprised by a playmate who approaches him stealthily from behind, but did you ever try the same game with a b.u.t.terfly? I have, many a time. After getting cautiously so near to a b.u.t.terfly at rest as to be able to distinguish between its head and its hinder extremity, I have quietly circled round it so as to approach it from behind, being at the time under the impression that it wouldn't see me under those circ.u.mstances. But not the slightest advantage did I derive from this stratagem, for the position and construction of its eyes enabled it to see almost all ways at once.

In addition to the two compound eyes, the _Lepidoptera_, or at least most of them, are provided with two small simple eyes; but these are generally so hidden among the closely set hair that covers the head, that it is doubtful whether they are of much service as organs of vision.

[Ill.u.s.tration: FIG. 5.--ANTENNae OF b.u.t.tERFLIES.]

[Ill.u.s.tration: FIG. 6.--ANTENNae OF MOTHS.]

The antennae proceed from two points close to the upper borders of the eyes. They are jointed organs, and are of very different forms in the various species of _Lepidoptera_. They are generally long, slender, and clubbed at the extremity in b.u.t.terflies, but exhibit several minor points of difference which we shall have to note later on. In moths the antennae are sometimes long, slender, and pointed. Some are thick, and more or less prismatic in form; while others are slightly or deeply pectinated or comb-like. The antennae of b.u.t.terflies are always straight, or only slightly curved; and, although the insects can sway them bodily, they have no power to bend them, or to stow them away in any place of shelter. Moths, on the other hand, when at rest, are almost invariably found to have their antennae snugly tucked under the wings, and brought so closely against the side of the head for this purpose that even the uncovered portion is often difficult to find.

There are two other prominent appendages belonging to the heads of the _Lepidoptera_. These are the _l.a.b.i.al palpi_ or feelers of the lips. They are generally easily seen, projecting forward on the under side of the head, sometimes so long and conspicuous as to give one the idea of a snout or long nose. The palpi are jointed--usually in three parts--are covered with scales, and often furnished with hairs or bristles.

If you watch a moth or b.u.t.terfly when it is feeding on the sweet juices of a flower, or on some kind of artificial sweet with which you have provided it, you will observe its long trunk or _proboscis_, by which food is sucked up. This instrument is so long and slender that it seems almost impossible that it can be a tube through which a liquid freely pa.s.ses. But a careful examination will show that this is the case. It is composed of two separate pieces--two half tubes, which, when closely applied to each other, form a very thin and flexible pipe, perfectly air-tight and adapted for suction. Sometimes you can see a b.u.t.terfly or moth manipulating with its proboscis as if it required readjustment in some way or other. It has split the tube throughout its length, so that it now looks like two exceedingly fine hairs. Then, after a short time, the two halves are put together again, and immediately, as if by magic, become a single tube in which no kind of seam is to be observed without a powerful magnifier.

In order to observe the nature of such a wonderful arrangement we must have recourse to the aid of a good microscope. Thus a.s.sisted, we can see at once how the junction of the two sides of the proboscis is brought about so quickly and so perfectly. The inner edges of each half are very regularly fringed with lines of closely set hairs--so regular, in fact, are they, that they give one the idea of long yet minute beautifully formed combs. When the two parts are brought together, the hairs of two opposite edges interlock, those on one side exactly filling the s.p.a.ces between those of the other.

The microscope also reveals another interesting fact, viz. that the proboscis is not a single tube, but, although so remarkably thin, is really a set of three distinct pipes, one lying on each side of the central one. It is said that the central tube only is used for sucking up the liquid food, and there seems to be some doubt as to the uses of the other two. Some naturalists are of opinion that the latter are air tubes, and are connected with the respiration of the insect; while others say that through these the insects eject a thin watery fluid with which to dissolve or dilute those sweetmeats that are not sufficiently liquid to be readily sucked up. But possibly both these opinions are correct, the proboscis serving all three of the purposes here named. The only observation of my own bearing on the subject is this. While a moth was feeding on a drop of syrup in a strong light, a powerful lens revealed drops, of liquid, mingled with bubbles of air, pa.s.sing alternately _up and down_ the two lateral tubes of the proboscis. At the same time the upward current of syrup in the central tube was by no means steady and continuous.

[Ill.u.s.tration: FIG. 7.--SECTION OF THE PROBOSCIS OF A b.u.t.tERFLY.]

When this organ is not in use, it is beautifully coiled into a close spiral which lies between the l.a.b.i.al palpi. The length varies considerably in different insects, and consequently the number of turns in the spiral must differ also. Sometimes there are less than two turns, while some of the longer ones form spirals of from six to ten turns.

In concluding our brief account of the head of lepidopterous insects it is, I suppose, hardly necessary to add that there is no kind of chewing apparatus to be described; all the members of this order, at least in the perfect state, deriving the whole of the little nourishment they require entirely by suction through the proboscis or 'trunk.'

The second division of the body is the _thorax_. This is much larger than the head, and consists of three ring-like segments, joined one behind the other so intimately that the lines of junction are hardly visible, even after the thick clothing of fine hair has been brushed off. Behind the thorax is the abdomen, which is composed of several segments, the junctions between the rings often being most distinct.

From the sides of the thorax proceed the two pairs of wings, the general structure of which we have already to a certain extent examined. But when we are a little farther advanced in our insect studies, we shall have to become acquainted with detailed descriptions given as aids to the identification of species. Now, such descriptions cannot be satisfactory, either to the one who gives or to him who receives, unless expressed in such definite terms as render a misunderstanding impossible. A botanist cannot give an accurate and concise description of a flower without the use of certain names and expressions which have gradually become an almost necessary part of his vocabulary; neither can an entomologist give a really useful, and, at the same time, a _succinct_ description of an insect unless he is acquainted with the names of its parts. Therefore, seeing that we distinguish the various species of b.u.t.terflies and moths _mainly_ by the arrangement and colour of the markings of their wings, it is really necessary that we should know the names of the different parts of these organs. For this reason I have inserted drawings of a fore and of a hind wing of a b.u.t.terfly, together with the names of the various parts of the wings, and also the names of the princ.i.p.al rays or _nervures_. Yet I would not advise any young entomologist to attempt to commit to memory all the names given.

Rather use the diagram for reference when occasion requires, more particularly when you have an insect in your possession that you desire to study. In ordinary descriptions of b.u.t.terflies and moths the names of the _nervures_ are not so generally used as those of the _parts_ of the wing. Consequently it is exceedingly useful to know what is meant by the terms _base_, _costal margin_, _apex_, _hind margin_, _a.n.a.l angle_, _inner margin_, _discoidal cell_ &c. as applied to the wing.

The two pairs of wings are attached to the second and third segments of the thorax; but of the _three_ pairs of legs, which we have next to consider, one pair arises from each of the three segments. The arrangement of these limbs is well shown in the sketch on page 3, as are also the names of the different parts of the limb, the latter being given for reference by the reader when the need arises.

All insects, in their perfect state, we are told, have three pairs of legs; but if you examine the under surface of certain b.u.t.terflies, such as the Marbled White, or any of the Vanessas, Browns, or Heaths, it is quite likely that you will raise objection to such a statement; for in these you may possibly see only four legs. But this is the result of a too cursory observation. Look a little more closely at your specimen, and you will see a pair of smaller legs folded up under the fore part of the thorax. By means of a blunt needle you can straighten out these limbs, and then the difference in length to be observed between them and the other four is very striking indeed. They are also thinner than the middle and hind legs; and, unlike these, are not provided with claws.

[Ill.u.s.tration: FIG. 8.--DIAGRAM OF THE WINGS OF A b.u.t.tERFLY.