New Zealand Moths and Butterflies/Micropterygina
Not dealt with in this volume.
Not dealt with in this volume.
The following are the principal characters of the Micropterygina:—
"In the two families, which constitute this highly interesting group, is fortunately preserved a type of Lepidoptera whose existence could never have been inferred from a study of other forms. Without a knowledge of these two families the true origin of the order could never have been more than a matter of more or less probable conjecture. The Micropterygidæ are the primeval ancestors of all the Lepidoptera, indicating their origin from the Trichoptera so nearly that one or two more discoveries might make it hard to draw any line of demarcation. The Hepialidæ are an offshoot from the Micropterygidæ (with considerable extinction of intermediate forms), constituting a separate line of development quite unconnected with any other Lepidoptera; if, as is possible, this separate stem may have ever given rise to other branches forming distinct families, all trace of their existence seems to have been lost.
"Imago with fore-wings and hind-wings more or less semi-oval, termen and dorsum forming a nearly uniform curve.
"Larva with few hairs, with 10 to 16 prolegs, or apodal, living concealed.
"Pupa in Hepialidæ with segments 7 to 11 and in male 12, in Micropterygidæ with all segments free."—(Meyrick.)
In this work the Hepialidæ alone are dealt with, the Micropterygidæ being reservedfor a future work. It may, however, again be mentioned that the last-named family contains amongst its New Zealand representatives Palæomicra chalcophanes, a species which more closely approximates in structure to a Neuropterous insect than does any other member of the Lepidoptera. This insect is consequently regarded by Mr. Meyrick as the most ancient species of the order yet known. The survival of Palæomicra in New Zealand is quite in accord with the existence of such forms as Apteryx and Dinornis amongst the birds, the tuatara lizard (Sphenodon) amongst reptiles, and Peripatus amongst Myriapoda, archaic forms which have been preserved in this country through its long isolation from continental areas, and the resulting absence of more recent competing forms.
"By no means an extensive family, yet of universal distribution. It stands more conspicuously isolated than any other group of Lepidoptera, for although it is without doubt a terminal development from the Micropterygidæ (that is one from which no existing family has originated), the gap between them is considerable; exotic genera, whilst differing in various details, are remarkably uniform in the more important peculiarities of structure, and do not at all tend to bridge the gap. The relatively large size of the Hepialidæ (of which some species exceed six inches in expanse of wing) may be attributed to the larval habits, which render these insects independent of the seasons or fluctuations of food-supply, thus removing the check which ordinarily limits growth. The modified type of neuration may have resulted directly from the increase of size, involving a great strengthening of the main veins beneath the costa to support the weight. As a consequence of this strengthening, the flight of the larger species is very powerful, and to this, combined with a choice of larval food, which is often rather indiscriminate, may perhaps be ascribed the wide range of the group, rather than to its antiquity. It is probably of Indo-Malayan origin, and must have existed in that region long enough to acquire fixity of type before its dispersal, which, geologically speaking, may not have been exceedingly remote."—(Meyrick.)
There are two genera represented in New Zealand.
1. Hepialus.2. Porina.
Genus 1.—HEPIALUS, F.
"A genus of universal distribution, but not very numerous in species. Ovum spheroidal, smooth. Larva elongate, active. Pupa with segmental whorls of spines, enabling it to move actively before emergence."—(Meyrick.)
Represented by one species only—the largest moth we have in New Zealand.
HEPIALUS VIRESCENS, Dbld.
This large and conspicuous insect appears to be generally distributed throughout the North Island.
The species is rather variable in both sexes. In the male the white spots on the fore-wings vary considerably in size, and there are occasionally several additional spots near the body. In the female the black markings of the fore-wings are sometimes much more extensive than the green ground colour. This dark form of the female was described by Butler as a distinct species, under the name of Charagia hectori. In both sexes the green colouring is occasionally entirely absent, a dull orange-brown taking its place. I formerly attributed this peculiarity to the effects of fading, but Mr. Norris has shown me a very perfect specimen of this variety, which he bred from the pupa, he having noticed the orange-brown colouring immediately after the insect emerged.
The transformations of this insect are very interesting. The female lays an enormous number of very small, round, yellowish eggs, which she seems to deposit quite indiscriminately. The young larvæ consequently have to find their way along the ground to the stems of their food-plant, a large percentage no doubt perishing before they succeed in doing so, and this circumstance probably accounts for the great number of eggs produced.
The food-plants of this species are numerous; the following are a few of them: "wineberry" or "currant" (Aristotelia racemosa), apparently the favourite; "manuka" (Leptospermum ericoides); "ki-ki" (Astelia solandri); "black maire" (Olea apetela); titoki (Alectryon excelsum); and Melicope. The larva tunnels the stems of these trees, feeding entirely on the wood, which it bites off with its strong mandibles.
For the most part it inhabits the main stem of the tree, its gallery always having an outlet, which is covered with a curtain of silk and refuse, and is spun exactly level with the surrounding bark, and very inconspicuous. These burrows usually run towards the ground, and are mostly two or three inches from the surface of the trunk. In some instances the larvæ inhabit branches, in which case, if they are small, the tunnels are made near the centre. Later on in its life, but probably some time before its transformation into the pupa, the caterpillar of this insect constructs a far more complicated burrow than the above. It consists of a spacious, irregular, but shallow cavity, just under the bark, having a very large opening to the air, which is entirely coveredwith a thin silken curtain, almost exactly the same shape and size as the numerous marks occurring at intervals on the trunks of many of the trees. Three large tunnels open into this shallow cavity: one in the centre, which runs into the middle of the stem, and one on each side, which run right and left just under the bark. These lateral tunnels are usually very short, but sometimes they extend half-way round the tree, and occasionally even join one another on the opposite side. The central tunnel has a slightly upward direction for a short distance inwards, which effectually prevents it from becoming flooded in wet weather; afterwards it pursues an almost horizontal course until it reaches the centre of the tree, when it appears to suddenly terminate. This, however, is not the case, for, if the gallery floor be carefully examined a short distance before its apparent termination, a round trap-door will be found, compactly constructed of very hard, smooth silk, and corresponding with the surrounding portion of the tunnel so exactly that it almost escapes detection. When this lid is lifted a long, perpendicular shaft is disclosed, which runs down the middle of the tree to a depth of 14 or 16 inches, and is about ½ inch in diameter. The upper end of this shaft is lined with silk, which forms a framework on which the trap-door rests when closed. The lid itself is of a larger size than the orifice which it covers, and this makes it extremely difficult, if not impossible, to force it open from the exterior, especially as it always fits down very closely as long as the insect remains in its burrow. The object of this contrivance is, no doubt, to prevent the ingress of enemies, large numbers of spiders, slugs, wood-lice, and various orthoptera being frequently found in both central and lateral tunnels, but they are quite unable to pass the trap-door. The galleries of individual larvæ are all wonderfully alike, the only differences observable being in the length of the perpendicular shaft, and in the direction of the horizontal burrow, which is sometimes curved. These variations are usually caused by the presence of other tunnels in the tree, which the larva appears to carefully avoid; at least I have never known an instance where a larva has allowed its tunnel to communicate with another one, whether inhabited or otherwise.
The last act performed by the caterpillar, prior to undergoing its transformation, is the construction of the above-described trap-door at the top of its burrow. This done the insect retreats to the bottom, its posterior segment resting on the termination of the vertical gallery. In the course of a few days the skin is cast off and worked downwards to the bottom of the burrow, underneath the last segment of the pupa.
As development progresses in the pupa it becomes darker in colour, especially on the wing-cases, where, in some female specimens, the future black markings of the moth are quite discernible as long as two months before emergence. Other specimens remain pale in colour until within a fortnight or three weeks of the appearance of the imago, when the green colouring of the wings suddenly becomes visible through their semi-transparent envelopes.
When about to emerge the pupa works its way up the vertical tunnel by means of the above-mentioned hooklets, forces open the trap-door, and wriggles along the horizontal burrow until it reaches the air, only the last three or four segments remaining in the tree. Its anterior portions then break open and the moth crawls out and expands its wings in the ordinary way, resting on the trunk of the tree, until they are of sufficient strength and hardness for flight.
The perfect insect appears in October and November. Although it must be common, it is rarely seen; specimens are consequently best obtained in the pupa state and reared in captivity. The easiest way to find the pupa is to pass a straw into the horizontal burrow, and move it about until it touches the trap-door. The collector is at once apprised of this circumstance by a distinct hollow sound, produced by the straw when it comes in contact with the lid, which acts like a miniature drum. If no such sound is heard after moving the straw into every possible position, it may be assumed either that the insect has left the burrow, or that it is inhabited by a larva only. When, however, a pupa is actually discovered, a section of the tree-trunk should be cut out, extending from about two inches above the horizontal burrow to about one foot below it, and the log, thus obtained, taken home. Should a number of pupæ be found in one tree the whole trunk may then be taken, if practicable, and kept in a well-lighted room or a conservatory, until the enclosed insects emerge. The specimens usually come out of the pupa at about five or six o'clock in the evening, and if intended for the cabinet should be killed before dark, as they very soon injure themselves when flying.
The best time of year to obtain the pupa of this insect is during August and September, as most of the specimens are then in that condition. Apart from the indications above described, burrows containing larvæ may often be known by the fresh pellets of excrement which are present near the opening. The vacated burrows frequently have the remains of the old pupa shell at the entrance, and generally look gnarled and weather-worn. These indications are useful as guides to the collector before exploring the burrow with a straw in the manner above described.
This insect is much attracted by light, and in consequence sometimes enters shop-windows and houses. In fact nearly all the captured specimens are so taken, the moth being very rarely found in its native forests. This circumstance is no doubt due to its very perfect protective colouring which, notwithstanding its large size, causes it to be almost invisible, when resting on the branch of a tree. On one occasion I discovered a specimen in this situation; being obliged to leave it for a short time, I experienced the utmost difficulty in finding it again, although I had taken a special note of its position. This species appears to be much persecuted by insectivorous birds, as we may frequently see its large green wings lying on the ground, where they are very conspicuous.
Of this genus we have eight species in New Zealand.
PORINA DINODES, Meyr.
(Porina dinodes, Meyr., Trans. N. Z. Inst. xxii. 206.)
(Plate XIII., fig. 8.)
This handsome species was discovered at Invercargill by Professor Hutton.
Described and figured from a specimen in Mr. Fereday's collection.
PORINA MAIRI, Buller.
(Porina mairi, Buller, Trans. N. Z. Inst. v. 279, pl. xvii., Meyr., Trans. N. Z. Inst. xxii. 207.)
A single specimen of this fine species was discovered by Sir Walter Buller on the Ruahine Ranges, in the Wellington district, during the summer of 1867.
The type specimen of this species was unfortunately lost in the wreck of the barque 'Assaye' in 1890. I have copied the above from Sir Walter Buller's original paper, and it may be well to point out that his description proceeds from the termen to the base, being the reverse order to that followed by me in all the other descriptions in this work.
The so-called "vegetable caterpillar" (infested with the Sphæria fungus [Cordiceps robertsii]) is, I think, very probably the larva of this insect. It was formerly supposed to be the larva of Hepialus virescens; but I have pointed out elsewhere that this is certainly erroneous, the larva of H. virescens living in the stems of trees, and never going beneath the ground, even to pupate, whilst the "vegetable" larva is subterranean. The real point to be discovered is the precise species of Lepidoptera this caterpillar would develop into, if not attacked by the fungus; but at present no definite information has been obtained on the subject.
PORINA ENYSII, Butl.
(Porina enysii, Butl., Proc. Zool. Soc. Lond., 1877, 381, pi. xlii. 7. Porina enysii, Meyr., Trans. N. Z. Inst. xxii. 207.)
(Plate XIII., fig. 9 ♂, fig. 10 ♀.)
This species appears to be confined to the North Island, where it is rather rare.
This species varies a good deal in the extent of the darker markings, and number and position of the dull white spots. When alive it is usually very strongly tinged with pink.
The perfect insect appears in December and January, and frequents forests. It is especially fond of resting on the stems of tree-ferns in the daytime, where, however, it is extremely inconspicuous, and can only be discovered by very careful searching. It is also very partial to light, and specimens might perhaps be secured more plentifully, if a good attracting lamp were exhibited in a suitable locality.
PORINA CHARACTERIFERA, Walk.
(Hepialus characterifer, Walk., Suppl. 594. Oxycanus impletus, ib. 598. Porina characterifera, Meyr., Trans. N. Z. Inst. xxii. 208.)
(Plate XIII., fig. 11 ♂.)
This fine species has been taken in the North Island at Auckland, Kaitoke, and Wellington.
The perfect insect appears in October, November, and December. At present I am only aware of four specimens in collections, viz., two in the British Museum, taken at Auckland; one in Mr. Meyrick's collection, taken by Mr. H. B. Kirk on the Rimutaka Ranges, at an elevation of about 1,500 feet; and one kindly given to me by Mr. W. R. Morris, who took it at Wadestown, near Wellington. It is evidently a scarce species, but may be looked for in the forest districts of the North Island.
PORINA CERVINATA, Walk.
(Plate XIII., fig. 12 ♂, fig. 18 variety of ♀.)
This insect is fairly common, and generally distributed throughout the country. It is very abundant in the Manawatu district.
This species is extremely variable. In many cases a large number of the spots is wanting. Mr. Meyrick states that the northern specimens are more yellow-ochreous, and more distinctly spotted than the southern ones. He adds that "the ochreous forms are easily distinguished from other species by the numerous spots and the absence of a continuous pale discal streak; the fuscous forms are sometimes very similar in colouring to P. despecta, but they are distinctly shorter-winged, and the compound discal spots appear to be a good character."
I have taken several specimens of what appears to be a variety of this species on the Tableland of Mount Arthur. It is much paler than the typical form, the markings much less distinct, and the central portions of the fore-wings very pale yellow (see fig. 18).
The moth appears in October. It is very much attracted by light.
PORINA DESPECTA, Walk.
(Hepialus despectus, Walk., Suppl. 594. Porina despecta, Meyr., Trans. N. Z. Inst. xxii. 209.)
(Plate XIII., fig. 13 ♀.)
This species has occurred in the South Island, at Christchurch, the Otira River and Lake Wakatipu.
The perfect insect appears in January, and is usually taken at light.
PORINA UMBRACULATA, Gn.
(Pielus umbraculatus, Gn., Ent. Mo. Mag. v. 1. Porina umbraculata, Meyr., Trans. N. Z. Inst. xxii. 209.)
(Plate XIII., fig. 14 ♂.)
This species is probably common, and generally distributed throughout the country. It has been taken at Palmerston, North Wellington, Nelson, Christchurch, Invercargill and Stewart Island.
This species varies considerably in the depth of the ground colour, and in the number of the black dots. A blackish shaded line, parallel to the termen, is also frequently present. The species may, however, be at once recognised by the straight, white, central stripe of the fore-wings.
The perfect insect appears from October till January, and is generally captured at light.
PORINA SIGNATA, Walk.
(Elhamma signata, Walk., Bomb. 1563. Porina novæ-zealandiæ, ib. 1573. Porina signata, Meyr., Trans. N. Z. Inst. xxii. 210.)
Apparently an abundant species in the North Island, having been takencommonly at Napier, Palmerston and Wellington. I suspect it occurs in the South Island also, but I have no records of its capture there.
I have often found a large subterranean caterpillar, that I believe to be the larva of this insect; but as I have never succeeded in rearing a specimen, I cannot assign it to this species with absolute certainty.
This larva is very lively when disturbed. It usually disgorges a large quantity of black juice from the mouth, biting meantime, in order no doubt to frighten its enemies. It feeds on the roots of various grasses.
The perfect insect appears in January, February and March, and is often extremely abundant at light.
- 'Entomologist,' xviii. 36.
- Since writing the above I understand from Mr. Baunehr that he has met with several specimens of this species in forest on the Dun Mountain, Nelson, at an elevation of about 2,000 feet.