Part 2

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 {xv}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_.

{xvi}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.)

{xvii}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.

{xviii}"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:--

"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

{xix}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.

{1}NEW ZEALAND

MACRO-LEPIDOPTERA.

I.--THE CARADRININA.

The _Caradrinina_ may be distinguished by the following characters:--

"The maxillary palpi are obsolete, the fore-wings have vein _1b_ simple or hardly furcate, _1c_ absent, and 5 approximated to 4 towards base. The hind-wings are furnished with a frenulum, vein _1c_ is absent, and 8 is connected or anastomosing with cell." (See Plate II., figs. 1 to 12 and 14 to 18.)

"Imago with the fore-wings more or less elongate-triangular, termen not very oblique; hind-wings broad-ovate.

"Larva sometimes very hairy, usually with 10 prolegs, those on segments 7 and 8 sometimes absent. (Plate III., figs. 7, 8, 9, 10, 11, 15 and 16.) Pupa with segments 9 to 11 free; not protruded from cocoon in emergence."--(Meyrick.)

So far as New Zealand is concerned, the _Caradrinina_ may be said to comprise that group of the Lepidoptera formerly known as the _Noctuina_, with the addition of the family _Arctiadæ_. Its members are chiefly nocturnal fliers; the body is usually stout, the forewings are narrow, and (except in the _Arctiadæ_) mostly dull-coloured, with three very characteristic spots. 1. The orbicular stigma, a round spot situated near the middle of the wing; 2. The claviform stigma usually somewhat club-shaped and situated immediately below the orbicular; and 3. The reniform stigma, a kidney-shaped marking situated beyond the orbicular. The claviform is very frequently absent, and the orbicular less frequently so, but the reniform is an almost constant character throughout the entire group, with the exception of the _Arctiadæ_.

There are three families of the _Caradrinina_ represented in New Zealand, viz.:--

1. ARCTIADÆ. 2. CARADRINIDÆ. 3. PLUSIADÆ.

Family 1.--ARCTIADÆ.

The _Arctiadæ_ may be characterised as follows:--

"Eyes smooth. Tongue developed. Posterior tibiæ with all spurs present. Hind-wings with veins 6 and 7 connate or stalked (rarely approximated or coincident), 8 anastomosing with cell nearly or quite from base to middle or beyond."--(Meyrick.) (See Plate II., figs. 1, 2, and 4, 5.)

This interesting family, although generally distributed throughout the world, is very poorly represented in New Zealand. Unlike most of the _Caradrinina_, many of the included species are day fliers and gaily coloured. One of these, _Nyctemera annulata_, is probably one of the most familiar of New Zealand insects, whilst the four remaining representatives of the family are but seldom seen. To British entomologists the name of {2}"tiger moths" will probably at once recall several conspicuous and beautiful members of this family.

Three genera of the _Arctiadæ_ are represented in New Zealand, viz.:--

1. NYCTEMERA. 2. UTETHEISA. 3. METACRIAS.

Genus 1.--NYCTEMERA, Hb.

"Tongue well developed. Antennæ in [M] bipectinated throughout. Palpi moderately long, porrected or rather ascending, with appressed scales; terminal joint moderate, cylindrical. Forewings with vein 6 out of 9 or separate, 7 and 8 out of 9, 10 connected with 9 by a bar. Hind-wings with veins 6 and 7 stalked or separate, 8 anastomosing shortly with margin of cell near base." (Plate II., fig. 3 head, 4 neuration of fore-wing, 5 ditto of hind-wing.)

"The single New Zealand species is endemic, but nearly allied to an Australian form."--(Meyrick.)

NYCTEMERA ANNULATA, Boisd.

(_Leptosoma annulata_, Boisd., Voy. Astr. v. 197, pl. v. 9; Dbld., Dieff, N. Z. ii. 284. _Nyctemera doubledayi_, Walk., Bomb. 392. _Nyctemera annulata_, Meyr., Proc. Linn. Soc., N.S.W., 1886, 700; ditto, Trans. N. Z. Inst. xxii. 218.)

(Plate IV., fig. 1 [M], 2 [F]; Plate III., fig. 9, larva.)

This species is perhaps one of the best known of the New Zealand Lepidoptera, occurring in great profusion in all parts of both North and South Islands. It is also common at Stewart Island, in the neighbourhood of cultivation.

The expansion of the wings is about 1¾ inches. _All the wings are deep sooty black. The forewings have an irregular cream-coloured band running from beyond the middle of the costa towards the tornus._ This band is interrupted in the middle, and crossed by several black veins, which sometimes almost break it up into a chain of spots. The hind-wings have a single large cream-coloured spot near the middle. The body is black, with several orange markings on the thorax, and a series of broad orange rings on the abdomen.

This species varies a good deal in the extent of the cream-coloured markings.

The larva feeds on the New Zealand groundsel (_Senecio bellidioides_), but in cultivated districts it is more often observed on _Senecio scandens_, a plant having a superficial resemblance to ivy, which frequently grows in great profusion on fences and hedgerows in various parts of the country.

Mr. W. W. Smith informs us[4] that it also feeds on the common groundsel (_S. vulgaris_) as well as on _Cineraria maritima_. I have often seen these caterpillars on mild days in the middle of winter, and full-grown specimens are very common towards the end of August, so that I think there is little doubt that the species passes the winter in the larval condition. At other seasons there is a continuous succession of broods.

The length of the caterpillar when full grown is 1½ inches. It is covered with numerous tufts of long black hair, and is black in colour, with the dorsal and lateral lines dark-red. There are several large blue spots round the middle of each of the segments, and the membrane between each segment is bluish-grey. In younger larvæ the bluish-grey colouring extends over a considerable portion of the insect.

This caterpillar may be readily found, as it feeds on the upper surface of the leaves fully exposed to view. Its hairy armour evidently renders it unpalatable to birds, and hence the secret habits we observe in most larvæ are absent in this species.