New Zealand Moths and Butterflies/Introduction
INTRODUCTION.
The order Lepidoptera, which includes all those insects commonly known as Moths and Butterflies, is chiefly distinguished by its members possessing four wings clothed with numerous minute scales, the term Lepidoptera being derived from the two Greek words, λεπις, a scale, and πτερον, a wing. The mouth of these insects is suctorial, the maxillæ forming a spiral proboscis which is coiled up between the large labial palpi when not in use (see Plate I., figs. 5 and 6). The other oral organs are rudimentary. To acquire this form these insects pass through three very distinct stages, viz., the Egg, the Larva, and the Pupa.
I.—METAMORPHOSIS.
THE EGG.
The eggs of Lepidoptera are generally somewhat globular, much flattened above and beneath. Some are very elaborately sculptured, whilst others are quite smooth. They are usually white or yellowish, but always change much in colour as the contained embryo develops.
THE LARVA.
The larvæ of moths and butterflies are popularly known as caterpillars. They always consist of thirteen segments, segment number one being the head. The head is furnished with several simple eyes (Plate I., fig. 2, AA), a pair of very short antennæ (BB), and a very powerful masticatory mouth. The mouth consists of the following organs: The labrum, or upper lip (1); a pair of mandibles, or upper jaws, working like scissor-blades (2,2); two maxillæ, or lower jaws (3,3), each carrying a jointed organ termed the maxillary palpus; and the labium, or lower lip (4); which bears another pair of minute jointed appendages—the labial palpi.
Segments 2, 3, and 4, which answer to the thorax of the perfect insect, are each furnished with a pair of legs. They consist of the six following joints (fig. 2): (a) coxa, (b) trochanter, (c) femur, (d) tibia, (e) tarsus, and (f) claw. These legs correspond to those of the perfect insect. The remaining nine segments of the body constitute the abdomen. Usually segments 7 to 9 and 13, each have a pair of fleshy pads, which are termed prolegs and are furnished on their edges with a row of minute hooklets (see Plate I., fig. 14, proleg highly magnified). It is these hooklets which enable caterpillars to hold on by means of their prolegs with such great tenacity. The number of the prolegs varies considerably in different groups and families.
The spiracles, or orifices of the air-tubes, are situated on each side of the larva just above the legs. They are usually present on segments 2 and 5 to 12, but vary considerably in different groups and families. The larva is provided with a very complete digestive system, which consists of the following organs (see Plate I., fig. 9): A, the œsophagus; D, the ventriculus; F, the clavate intestine; E, the ilium; H, the colon; K, the biliary vessels; and O, the spinning vessels. These last open at a small orifice in the labium termed the spinneret (fig. 2, 5). They supply the silken threads which are employed by most larvæ in constructing their cocoons, and which also serve in cases of danger as a rapid means of retreat. Many larvæ, which live on shrubs and trees, suddenly lower themselves to the ground by means of one of these silken threads, and thus often escape being devoured by insectivorous animals.
The entire growth of the insect is accomplished during the larval condition, the increase in size being frequently very rapid. Owing to this circumstance larvæ are often compelled to shed their skin, and in many species a very considerable alteration both in the shape and colour takes place at each moult, or ecdysis as it is sometimes termed.
THE PUPA.
The pupa of a Lepidopterous insect is completely encased in a chitinous envelope. With the exception of a slight twirling of the abdominal segments it is incapable of any motion. In the pupa of Micropteryx the mandibles and labial palpi are said to be functionally active, but this is a very exceptional though extremely interesting case. In conjunction with other evidence it would appear to indicate that the Lepidoptera originated from insects with active pupæ. The number of free or movable segments of pupæ varies considerably in different groups and genera, and by some modern authors it is regarded as a character of much importance in the framing of their classifications. The various organs of the perfect insect are distinctly marked out on the otherwise uniform integument of the pupa. In some groups, notably the Micropterygina, these organs are much more distinctly indicated than in others.
II—ANATOMY.
THE PERFECT INSECT OR IMAGO.
In common with all other members of the class, the body of a Lepidopterous insect consists of three main divisions: (1) the head, (2) the thorax, and (3) the abdomen.
THE HEAD.
The front of the head is termed the face, the top the crown, the sides are nearly entirely occupied by the compound eyes (Plate I., fig. 11, AA), and the lower surface by the organs of the mouth.
The Eyes consist of a very large number of simple lenses arranged in the form of two hemispheres, one on each side of the head. The ocelli, or simple eyes, are situated on the crown, and are usually almost entirely covered by scales.
The Antennæ are two jointed appendages attached to the top of the head above the eyes. They vary very much in structure. The following are the terms used in describing the different forms of antennæ in the Lepidoptera:—
1. Pectinated, when the joints have long processes like the teeth of a comb. If these are on one side only, the antennæ are unipectinated; if on both sides, bipectinated. (Plate I., fig. 20, bipectinated antenna of Nyctemera annulata.)
2. Dentate, when the joints are armed with slight pointed spines.
3. Serrate, when the joints have sharp projections like the teeth of a saw. (Fig. 18, antenna of Melanchra composita.)
4. Filiform, when the whole antenna is simple or thread-like. (Fig. 19, antenna of Epirranthis alectoraria.)
The clothing of the antennæ also varies, and is distinguished as under:—
1. Ciliated, when clothed with one or two series of short, fine hairs.
2. Fasciculate-ciliated, when the hairs are collected into tufts. (Fig. 17, antenna of Chloroclystis plinthina.)
3. Pubescent, when the antennæ are clothed with uniform short hairs. (Fig. 19.)
The functions of the antennæ are still a matter of dispute amongst entomologists. The majority of the older naturalists regarded them as organs of hearing. The antennæ are almost always more fully developed in the male than in the female. From this circumstance many modern entomologists consider that one of their functions is to enable the former to find the latter.
The organs of the mouth are thus distinguished:—
1. The Labrum, or upper lip (Plate I., fig. 11, l), a minute rudimentary plate situated in front immediately above the proboscis.
2. The Mandibles, or upper jaws (m.m), two minute sickle-shaped organs situated just below the labrum, also rudimentary.
3. The Proboscis, or Haustellum[1] (c), a tubular extensible organ formed of the two maxillæ, or lower jaws, which have become greatly elongated, semi-tubular, and closely pressed together at the edges, but separable at the will of the insect—a structure which enables the organ to be easily cleansed when necessary, and is extremely interesting as indicating so clearly the true development of the proboscis from the maxillæ.
The Maxillary palpi (p.p) are two jointed organs attached to the base of the proboscis and very frequently rudimentary, but fully developed amongst certain of the Micro-Lepidoptera.
The Labium, or lower lip, is situated below the proboscis and carries the Labial palpi (figs. 5 and 6), two large jointed organs which are very conspicuous in nearly all the species and often quite conceal the maxillary palpi. They are usually regarded as organs of touch, but their true function does not seem to be properly understood. In the Lepidoptera they appear to protect the proboscis, which, when out of use, is always coiled up in a spiral between them. The labrum and mandibles can only be seen by removing the large labial palpi.
THE THORAX
carries the organs of locomotion, which consist of two pairs of wings attached to its sides, and three pairs of legs attached beneath, a pair belonging to each of the three segments of which the thorax is composed. On the front of the thorax there are two flap-like organs covered with scales, termed the patagia.
The Wings vary greatly in shape, but usually they are triangular. The portion of the wing which joins on to the thorax is termed the base. The front margin is called the costa, the outer margin the termen, and the lower margin the dorsum, these being described as situated when the wing is extended in flight. The angle between the costa and termen is called the apex, and the angle between the termen and the dorsum the tornus (see Plate I., fig. 1). The termen and dorsum are edged with a fringe of hair-like scales, termed the cilia. At the base of the hind-wings is generally situated a stiff bristle, or several stiff hairs, called the frenulum, the ends of which pass through a chitinous process on the under side of the fore-wing near the dorsum. This process is termed the retinaculum, and serves, in conjunction with the frenulum, to lock the wings together during flight. In the female both these organs are often very imperfectly developed, the frenulum consisting of several bristly hairs, and the retinaculum of a group of stiff scales. In many of the Lepidoptera both frenulum and retinaculum are entirely wanting.
"In the Micropterygina, a membranous or spine-like process called the jugum rises from the dorsum of the fore-wing near the base and passes under the hind-wing, which is thus held between the process and the overlapping portion of the fore-wing."—(Meyrick.)
The veins of the wings are thus described by Mr. Meyrick:—
"The wings are traversed by a system of Veins—tubular structures which serve at once as extensions of the tracheal system, and to form a stiff framework for the support of the wing. In the normal type of Lepidoptera the fore-wings possess three free veins towards the dorsum, termed 1a, 1b, and 1c; a central cell, out of which rise ten veins, numbered 2 to 11, the sides of the cell being known as the upper median, lower median, and transverse veins respectively; and a free subcostal vein, numbered 12; whilst the hind-wings differ from the fore-wings in having only six veins rising from the central cell, numbered 2 to 7, so that the free subcostal vein is numbered 8 (see Plate I., figs. 3 and 4, assumed type of neuration of a Lepidopterous insect). In some forms a forked parting-vein traverses the middle of the cell longitudinally, and a second parting-vein traverses the upper portion, so as to form a secondary cell; but these are more frequently absent or represented only by folds in the membrane. In a few forms there is a tendency to the production of several false veins, termed pseudoneuria, appearing as short branches from the subcostal vein of the hind-wings to the costa; these are thickenings of the membrane, and are commonly very irregular and variable, often uneven in thickness or incomplete. Sometimes one of these near the base is better developed and more permanent in character; it is then termed the præcostal spur (see Plate I., figs. 89 and 279). Modifications in the general arrangement of the veins may arise through any of the following processes, viz.: (1) obsolescence, when a vein loses its normal tubular structure, becoming attenuated and reduced in substance, until it appears a mere fold of the membrane (Plate II., fig. 60, vein 5 in hind-wings of Selidosema); (2) stalking, when the two veins are fused together for a portion of their length from their base, so as to appear to rise on a common stalk (Plate II., fig. 34, veins 6 and 7 in hind-wing of Hydriomena); (3) coincidence, when two veins are fused together for the whole of their length, so that one appears entirely absent, an extreme form of stalking; (4) anastomosis, when two veins rise separate, meet, and are fused together for a certain distance, and then separate again (Plate II., fig. 23, veins 7 and 8 in the hind-wings of the ♀ of Tatosoma); (5) concurrence, when a vein rises separate, runs into another, and does not separate again, an extreme form of anastomosis; (6) connection, when two veins are connected by a short transverse bar passing from one to the other, a special form of anastomosis, evolved from the ordinary form under the influence of a tendency to lateral extension (Plate II., fig. 28, veins 7 and 8 in hind-wing of Paradetis). Vein 1b in both wings is often furcate at the base.
"The type of veins in the Micropterygina differs from that described above in two essential particulars, viz.: (1) there may be three additional veins in the fore-wings, rising out of vein 11 or 12; and (2) the veins of the hind-wings are practically identical in number and structure with those of the fore-wings, being thus much more numerous than in the ordinary type. There is also often a system of cross-bars between the veins near the base of the wing (Plate I., figs. 22 and 23, neuration of Hepialus).
"The structure of the veins can be best observed on the under surface of the wing, where they are more prominent. The student should begin by completely denuding of scales a few wings of common species: the wing should be cut off and laid on a moistened piece of glass, to which it will adhere; the scales should then be removed, first from one surface and then from the other, with a fine, moist camel's-hair brush—an operation requiring a little patience and delicacy of touch; the veins will thus be rendered conspicuous.[2] When, however, the student has familiarised himself with the general subject, it will not be found necessary in practice to resort to this process; most details will be easily observed without denudation[3]; where this is not the case (as where the veins are closely crowded or otherwise obscured), the scales can be removed with the brush on the under surface in the locality of the difficulty only, without cutting off the wing or otherwise damaging the specimen, which remains in the collection available for all purposes as before; with proper practice, even the smallest species are amenable to this treatment, which does not require more skill than the actual setting of the specimen. Some workers prefer to put a drop of benzine on the spot, which renders it temporarily transparent; the effect is short-lived, as the benzine evaporates rapidly, and the cilia (if long) are liable to be damaged by this method."
The Legs consist of the following joints (see Plate I., fig. 21): (1) coxa, (2) trochanter, (3) femur, (4) tibia, (5) tarsus, (6) claw. The tarsus normally consists of five joints, but is more or less aborted when the leg is not employed for walking. The spines (SS) on the tibiæ of the several legs vary considerably in size and number. They are often useful to the systematist for purposes of classification.
THE ABDOMEN
consists of nine segments, some of which are often fused together. It contains the various internal organs, of which the most important are those of Digestion and Reproduction. The Digestive System (Plate I., fig. 10) consists of the following organs: A, the œsophagus, or throat; C, the sucking stomach; D, the ventriculus or stomach; E, the small intestine; G, the cæcum; H, the colon; K, the biliary vessels; N, the salivary vessels. The function of the sucking stomach is to exhaust the air in the throat and proboscis, and thus to cause the ascent of the fluids into the stomach when the insect is feeding.
III.—ORIGIN OF SPECIES.
The theory of the origin of species as propounded by Darwin may be thus very briefly summarised:—
Variation.—No two organisms are exactly alike; there is always some variation from the parent form, in some cases very slight, in others considerable. (For examples of variation see Plate VII., figs. 1 to 9, varieties of Hydriomena deltoidata; Plate VIII., figs. 42 to 47, varieties of Epirranthis alectoraria; Plate IX., figs. 6 to 14, varieties of Selidosema productata; Plate X., figs. 13 to 23, varieties of Azelina gallaria; Plate X., figs. 39 to 47, varieties of Declana floccosa.)
Inheritance.—Many of these variations are inherited—a fact demonstrated by our domestic plants and animals, where man has selected and bred from varieties suitable for his purposes, and has thus produced races in which the variation is permanent. Many of the races of domestic animals differ as much from one another as do some distinct species of wild animals.
Struggle for Existence.—All animals and plants produce far more offspring than can possibly survive, thus giving rise to the struggle for existence. For example: The average number of eggs laid by a Lepidopterous insect is certainly over 100, and in many species this number is greatly exceeded. Assuming each female to lay 100 eggs, the progeny from a single pair would amount, after six generations, to over six million individuals.
Natural Selection, or the Survival of the Fittest.—In the struggle for existence which necessarily results from such a great increase of individuals, those variations which favoured the possessors would be preserved, whilst those which did not, would be gradually exterminated. This principle of the preservation of the favourable varieties in the struggle for life is called Natural Selection, or the Survival of the Fittest.
Divergence of Character.—As there are so many different places and conditions in the economy of nature which can be occupied by organic beings differently constituted, individuals which diverged most from the original type would be brought into less severe competition, than those which diverged only in a slight degree. For instance, if we represent the original form as A, occupying one place in the economy of nature; a second form as B, occupying a somewhat similar place; a third form as C, occupying a very different place to A although somewhat similar place to B, it is obvious that B would enter into severe competition with both A and C, whilst A and C might not trend to any great extent on one another's place in the natural economy; hence B would be exterminated before either A or C. In other words, natural selection continually tends to increase the slight differences, which we call varieties, into the greater differences, which we call species.
The following phenomena, which have long been observed by students of the Lepidoptera, will serve as excellent examples of the operation of natural selection:—
Protective Resemblance.—This term is applied to those classes of form or colour which enable an animal to so closely resemble its surroundings as to escape the notice of its enemies. Numerous examples of protective resemblance exist in the New Zealand moths and butterflies; in fact, it may safely be asserted that nearly all the colouring we observe in these insects has been acquired for protective purposes. The following species, amongst many others which will be described hereafter, exhibit in a very marked degree the phenomenon of protective resemblance: Epirranthis alectoraria, Selidosema dejectaria, and Drepanodes muriferata resemble dead leaves; Chloroclystis bilineolata, Tatosoma agrionata, and Erana graminosa resemble, when at rest, patches of moss; Selidosema productata and S. lupinata resemble the bark of trees; Chloroclystis lichenodes, Declana floccosa, and Elvia glaucata resemble variously coloured lichens. It is almost unnecessary to point out that all those variations, which tended to conceal the possessors from their enemies, would be preserved in the struggle for existence, and that these numerous and perfect instances of protective resemblance would inevitably result from the operation of natural selection. The dark colouration of Alpine and Arctic Lepidoptera, which enables them to rapidly absorb heat during the short and fitful gleams of sunshine experienced on mountains or in high latitudes, is also an instance of adaptation to conditions through the influence of natural selection. This was first pointed out by Lord Walsingham in 1885. The almost complete absence of white species in these localities is a good example of the extinction of forms unfitted to their surroundings.
Contrast Colours.—In this class of colouring the fore-wings only are protectively coloured, the hind-wings being very conspicuous. Contrast colouring is well exemplified by several of the insects included in the genus Notoreas. The sudden exhibition of the hind-wings during flight dazzles the eye of the pursuer. When the insect immediately afterwards closes its wings and the fore-wings alone are visible, it is extremely difficult to see. This form of protective colouring was also first drawn attention to by Lord Walsingham. (See page 75.)
Warning Colours.—Insects, which are unfit for food or nauseous, are not protectively coloured, but on the contrary are rendered as conspicuous as possible. This class of colouring is well illustrated by one of our commonest moths, Nyctemera annulata (Pl. IV., figs. 1 and 2). The principle of warning colours was first discovered by Mr. A. R. Wallace, and is graphically described in Professor Poulton's entertaining work, 'The Colours of Animals.' The possession of nauseous qualities would be of little value to an insect, unless it could be at once recognised by insectivorous animals and avoided as food. If a nauseous insect were not easily identified it would speedily be destroyed by what Professor Poulton ingeniously terms "experimental tasting"; hence, through the process of natural selection, all nauseous species have become very conspicuously coloured. It may be remarked that warning colours are extremely rare amongst the New Zealand species, and I am not aware of any other example than that already given.
Mimicry.—This term is applied to those remarkable cases where a harmless or edible species imitates in form and colouring a highly armed or nauseous species. No instances of this extremely interesting class of protection are yet known amongst the New Zealand Lepidoptera, but a very perfect example of mimicry exists between two common introduced species of Hymenoptera and Diptera, the well-known honey-bee and the drone-fly. The superficial resemblance between these two insects is very close. The bee, as every one knows, is armed with a powerful sting, whilst the drone-fly is unarmed. In this case it can be seen that if a harmless insect varied in the direction of resembling a formidable or objectionable species it would be a decided advantage to it, and such varieties would tend to be continually preserved and improved, through the operation of natural selection. The subject of mimicry has been alluded to here as it is not impossible that some instances of it may yet be discovered in connection with our native Lepidoptera.
Ornamental Colouring.—This class of colouring occurs in many species, especially amongst the butterflies, and is not apparently connected in any way with protection. Darwin supposes that it has arisen through the females of each species always selecting the most beautiful males as mates, hence these alone would leave progeny, and the females themselves would afterwards become beautiful through the effects of inheritance. This principle Darwin has termed Sexual Selection, and has discussed it in great detail in his work on the 'Descent of Man.' The fact, that amongst birds and butterflies the males are nearly always the most brilliantly coloured and the most beautiful, together with an immense mass of other evidence, tends, I think, to entirely support Darwin's theory, although it should be mentioned that several eminent naturalists, including Mr. Wallace, do not admit the principle of Sexual Selection.
IV.—CLASSIFICATION.
From a further consideration of the foregoing principles it will be seen that all existing species are held to be descended by true generation from pre-existing species, and that, consequently, all the relationships we observe between species are explained by community of origin. The most natural system of classification is, therefore, that which best reveals the scheme of descent, or, as it is termed, the phylogeny, of the group of organisms classified. To construct a perfect system of classification on these principles a knowledge of not only all the existing species of Lepidoptera would be essential, but also of all the extinct species, and it is needless to say that such knowledge is quite unattainable. Nevertheless large numbers of species are now known from many parts of the world, and a very extensive collection has recently been employed by Mr. Meyrick in framing a classification of the Lepidoptera, which is, to the best of my belief, the first constructed on strictly Darwinian principles. Although adopting Mr. Meyrick's system in the present work I do not agree unreservedly with all his conclusions; but I have not attempted to alter his system in accordance with my own views, as I conceive that the conclusions of a naturalist, who has only had the opportunity of studying a restricted fauna, would necessarily be liable to considerable error.
The general principles on which Mr. Meyrick has founded his system are practically those laid down by Darwin in his 'Origin of Species,' and may be thus summarised:—
A. Resemblances between all organisms are explained by community of origin, the amount of difference representing the amount of modification and expressible in the classification as varieties, species, genera, families, groups, orders, &c. The amount of difference does not necessarily bear any direct relation to time, many forms remaining almost stationary whilst others are undergoing development.
B. By a consideration of the following laws the age of a division can be approximately arrived at; that is to say, its position in the great genealogical tree of the Lepidoptera can be, to some extent, determined:—
"(1) No new organ can be produced except as a modification of some previously existing structure.
"(2) A lost organ cannot be regained.
"(3) A rudimentary organ is rarely redeveloped."—(Meyrick.)
C. The greatest care is necessary to avoid being misled by adaptive characters, i.e., characters which are very important to the welfare of the species, and hence much modified through the agency of natural selection. A familiar instance of superficial resemblance, due to the presence of similar adaptive characters, may be observed in fishes and whales, where two groups of animals with but little real relationship have, through living under similar conditions, become extremely like each other in external appearance. Other examples might be given amongst exotic Lepidoptera. Thus, many noxious species are closely mimicked by harmless forms which are often far removed from them in real affinity. These cases of adaptive resemblances abound amongst all organisms, and have often deceived experienced naturalists. It is in consequence of the illusive nature of these external resemblances amongst different members of the Lepidoptera, that the structure of the neuration of the wings is now considered of such great importance as a character for purposes of classification. The numerous modifications in the position of the veins and their presence or absence in certain groups can, so far as we are able to see, have had very little effect on the well-being of those insects possessing such modifications. Hence it may fairly be assumed, that these structures have been free from the influence of natural selection for a very lengthened period. It is thus contended that the neuration of a Lepidopterous insect probably reveals more plainly than any other character its true relationship with other species.
The descent of all the Lepidoptera from some ancient member of the Trichoptera (or caddis-flies) is thus proved, according to Mr. Meyrick:—
"From a consideration of the laws enunciated above, there can be no doubt that the Micropterygina are the ancestral group of the Lepidoptera, from which all others have descended; this is sufficiently proved by the existence of the four or more additional veins in the hind-wings of that group, for these veins, if not originally present, could not have been afterwards produced. Of the two families of that group, the Micropterygidæ, which possess an additional vein (or veins) in the fore-wings, and fully developed six-jointed maxillary palpi, must be more primitive than the Hepialidæ. Now if the neuration of the whole of the Lepidoptera is compared with that of all other insects, it will be found that in no instance is there any close resemblance, except in the case of the Micropterygidæ; but the neuration of these so closely approaches that of certain Trichoptera (caddis-flies) as to be practically identical. The conclusion is clear, that the Lepidoptera are descended from the Trichoptera, and that the Micropterygidæ are the true connecting link. If the other marked structural characters of the Micropterygidæ are taken into consideration, viz., the possession of the jugum, the large development of the maxillary palpi as compared with the labial, and the sometimes functionally active mandibles, they will be all found commonly in the Trichoptera, affording additional confirmation. It may be added that in one New Zealand species of Micropterygidæ (Palæomicra chalcophanes) vein 1b is basally trifurcate, a character frequent in the Trichoptera, but not yet discovered in any other Lepidopteron. In most Trichoptera the veins of the hindwings are much more numerous than those of the fore-wings, in the Micropterygina they are usually equal in number, in other Lepidoptera they are less numerous; in the course of descent there has therefore been a greater progressive diminution in the number of veins of the hind-wings as compared with those of the fore-wings, though these also have diminished.
"It is unnecessary to trace back the descent of the Lepidoptera further; but it may be worth while to point out that we may assume as the primitive type of Trichopterous neuration, a system of numerous longitudinal veins gradually diverging from the base, mostly furcate terminally, and connected by a series of irregularly placed cross-bars near base, and another series beyond middle."
The following is Mr. Meyrick's method of arrangement, which has been adopted in this book:—
"The natural order of arrangement, which is that of a much-branched tree, cannot be adequately expressed by a simple linear succession, such as is alone practicable in a book. It is, however, possible to devise a linear succession which shall be consistent with the natural genealogical order, if some additional explanation can be given. The method here adopted is as follows:—
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"Suppose the accompanying diagram represents a portion of the genealogical tree; then the order will begin at M and descend to K, recommence at L and descend to K, and thence to G, recommence at H and descend to G, and thence to B, recommence at F and descend to D, recommence at E and descend to D and thence to B, recommence at C and descend to B and thence to A, and so on. Thus the order begins with the most recently developed forms and descends gradually to the earliest or most ancestral, which are the last in the book. To understand the order in practice, it may be assumed that each genus is descended from that which immediately follows it in the book, unless its actual descent is expressly stated otherwise; such statement will, of course, require to be made before every recommencement of a fresh branch. This system has been adhered to throughout, and after a little use will not be found unintelligible. If adopted in the arrangement of a collection in the cabinet, it would be a good plan to indicate the recommencement of a fresh branch by a special mark, such as a red bar drawn above the first (or highest) species."
Phylogeny of Lepidoptera. (After Meyrick.)
| Notodontina | Papilionina | ||||
| Caradrinina | Lasiocampina | Pyralidina | |||
| Psychina | Tortricina | ||||
| Tineina | |||||
| Micropterygina | |||||
V.—GEOGRAPHICAL DISTRIBUTION.
The details of geographical distribution are given under the headings of the respective species, so far as I have been able to ascertain them; but our knowledge in this direction is necessarily limited, and I have found much difficulty in obtaining reliable information, on account of the obstacles which exist in regard to the correct identification of species in other countries.
The distribution of the species within New Zealand is also very imperfectly known at present, owing to the paucity of collectors and observers, particularly in the extreme north of New Zealand, and on the west coast of the South Island. In the latter locality no doubt many interesting species remain to be discovered, especially amongst the mountain ranges.
In employing the book for identifications, the reader is recommended to first refer to the Plates and see if he can find anything at all resembling the species he has, and then to refer to the description for verification. In dealing with variable forms, it is always well to remember that the shape of markings is generally far more constant than their intensity, or even their colour.
The purely descriptive portions of the work have been made as brief as possible, and characters, of special importance for the identification of species, are printed in italics. Those who desire to consult more detailed descriptions may readily do so by referring to Mr. Meyrick's papers, in the Transactions of the New Zealand Institute and elsewhere. References to such papers are invariably given under the synonomy of each species which has been described by Mr. Meyrick.
It should be mentioned that the figures and descriptions in this work have been prepared from nature, quite separately, and no attempt has been made to reconcile the figure with the description. This course has been followed so that any character, which may have been accidentally omitted from the figure, will not necessarily be wanting in the description.
The figures of neuration (Plates I. and II.) have all been made from fully denuded specimens examined under the microscope. They are in nearly every instance considerably enlarged. Each drawing has afterwards been compared with Mr. Meyrick's description, and if found to differ, a second examination of the wings has been made with a view to a reconciliation of results. Any important differences observed between Mr. Meyrick's descriptions and my final results are in every case specially mentioned.
- ↑ This organ is termed the tongue by Mr. Meyrick. As many mandibulate insects possess a true tongue, and the proboscis of the Lepidoptera is not homologous with the tongue, but with the maxillæ, I think the term is very misleading.
- ↑ For the examination of the wings taken from dried specimens, I have found that immersion in methylated spirits renders the veins visible after partial denudation with the camel's-hair brush. With recent specimens, however, the scales can easily be entirely removed.
- ↑ I have found considerable difficulty and uncertainty in examining the neuration of undenuded specimens.