Transactions and Proceedings of the New Zealand Institute/Volume 11/Article 29
Art. XXIX.—Notes on the Metamorphosis of one of our largest Moths—Dasypodia selenophora. By W. Colenso.
[Read before the Hawke Bay Philosophical Institute, 10th June, 1878.]
On the 21st January, 1878, my attention was called to an unusually large caterpillar, apparently asleep on the trunk of an Acacia tree (silver wattle). At first sight, it seemed so much like the bark of the tree in hue, that it was not readily distinguished from it. The larva was stretched out to its full length, nearly 3″ 6‴; it was elongate, and of the ordinary form, pretty evenly cylindrical throughout, though thickest in the middle and tapering towards its head and tail, and skin smooth. In colour, it was peculiarly mottled or finely speckled (irrorated) with very minute points of black, red (carmine), and ash colours—the latter predominating—which, combined, and at a little distance gave it the colour of the reddish-grey bark of the tree above-mentioned. It had two minute bright red (carmine) spots close together on its back, near the tail, and when in motion two large triangular dark splashes were displayed on its back; the colour of the belly of the larva was pale (dull white), with several round olive spots in pairs, corresponding to its belly feet. Its head was small, of a pale Indian-yellow colour; its hind feet were large, and it had also two broad anal feet.
On being touched, it coiled itself up very rapidly and closely. This it did many times, so that it was difficult to get to see its under parts. It did not seem inclined to crawl, and was very quiet. I put it under a large bell-glass, and tried it with various leaves, but it would not eat anything; so I left it, thinking it would shortly undergo its transformation.
The tree on which I found it was a large old one, and it was on its main stem about 4 feet from the ground; how it came there was a mystery, for there were no shrubs nor plants nor even grass near,—it being the very middle of our dry season (which this year was extreme), and while the upper overhanging branches of the tree were several feet above my head.
All that day and part of the next it remained very quiet, still keeping stretched out to its full length, but not moving; it ate nothing, though on the 22nd it discharged several large pellets (fæces), of an obtuse cylindrical shape.
I kept watching it daily, and on the 25th January I found it had spun a small white web (cocoon) with which it had managed to bring together and curl down around it the edges of a large leaf of the common red geranium, fastening also the leaf pretty closely to the sheet of paper below, so that I could not get a single glimpse of the larva, although I tried many ways; but as the weather was so hot and dry, and the leaf quickly withering, I soon left off making any further attempts to observe it, fearing I might injure the larva.
Several weeks passed and no sign of its change appeared; and I was almost getting tired of making so many diurnal visits, when, on the morning of the 21st of March, I found it had emerged a perfect insect, a large moth of wondrous beauty! I do not think that it had left its pupa-case during the night, as there was but a very small amount of its long downy covering about the glass; for had it done so, being a nocturnal creature and of a large size, it would surely have knocked itself about a good deal in its vain attempts to get out.
I may truly say that I gazed on it with pleasure and astonishment; fcr though I had pretty largely known our New Zealand Lepidoptera (having collected many hundreds of species some 25–40 years ago)[1] I had never before seen one like this. It differs too, very considerably from our British species, although I thought I had formerly seen something not altogether unlike it in books. There, however, it was, a handsome large black moth, forming almost an equilateral triangle of 1″.6‴ as it remained at rest. I knew that it belonged to the Noctuina group, but that was all. So I sent an outline of its appearance to Mr. Fereday, the celebrated entomologist residing at Christchurch, enquiring if there were any such specimens in the Museum there, or if he knew of such a moth. From Mr. Fereday I received a very kind and full reply, that, while there were no specimens of this moth in the Canterbury Museum, he had one (a female) in his own possession, which had been taken some years ago at Nelson; and that, though rare, the perfect insect had been described, and was the Dasypodia selenophora of Guenee.[2]
And now for a brief description of the perfect insect.
Its size across, with wings extended, is 3″ 3‴; length of body, 1″ 3‴; the body thick, with 7 segments, but tapering downwards rapidly from its second segment almost to a point at the tail (not unlike, in this respect, those well-known British species of the Sphingidæ family, Smerinthus tiliæ, and Chærocampa porcellus), and densely covered with very long down. Antennæ, nearly 1″ long, slender and evenly attenuated, but not smooth, being apparently very finely aud regularly ringed and serrulated; legs, large and stout.
Its colour, on the other side, when living, was a sooty black; but after death it changed to a dark umber colour, with dark zig-zag and other markings on its wings (somewhat resembling those on the wings of the Emperor Moth, Saturnia pavonia-minor), and with a peculiar large and lustrous ocellated spot on each fore wing near the costa—in a line with the anal angle; all the wings are ciliated, bearing minute whitish dots at the extremities of the nerves or rays just within the margin. Its colour on the under side was ochrous or fulvous; the legs, amber-coloured below the knee, but its thighs were ochrous, and thickly covered with excessively long and waving down; its horns also were ochrous coloured but darker at their bases.
While living, it was a truly superb, rich, velvety-looking creature; presenting, too, when at rest, such a regular and graceful equi-triangular outline. The eyes on its wings had (if I may so express myself) a living look, much as the irises of the eyes of men and animals are sometimes drawn when represented under bright light. Those spots, or eyes, were all alike, black, but the two circular rims round each, and the lunate or triangular iris-pupil-like part within were shining lustrous and waxy, or as if strongly gummed. What with its fine moony eyes on its wings, and its long wavy down on its thighs, it well deserved its expressive name, both generic and specific. I could not help thanking its describer, for it is not often that we find so fit and distinguishing a name given in these modern times, either to an animal or to a plant. Much, however, of its surpassing beauty quickly faded after death, which I attributed to the fumes of the sulphur I had used in killing it, not having any chloroform at hand, and leaving home on that very day by train to visit the country schools.
The pupa-case (after the moth had emerged) is nearly cylindrical, very obtuse at the head, and tapering regularly downwards from end of folded wings at 4th segment, and pointed conical at the tail; length, 1″ 3‴, and diameter in thickest part 6‴; suspended slightly by tail; well-marked in front with folds of wings and antennæ, eyes and head of imago, and very strongly with 7-ringed segments, each having two long spiracle marks, one on each side. Colour dark red (garnet), with a blueish or violet bloom (dust), but smooth and shining on its prominent parts.
Cocoon very small, white and coarse, almost woolly; just sufficient to hold the edges of the leaf down to paper, where, however, it was strongly fastened; fæcal pellets emitted after enclosure.
The imago had made its exit by a small round hole at the top of pupacase, back of the head, the case having also slightly given way down the costal marking of the wungs on each side.
Note.—Dr. Dieffenbach saw the moth I had raised from the larvæ referred to (in the note, p 301), at my house in the Bay of Islands, where he was a frequent visitor during his stay there in the summer of 1840–1841; and from me the doctor obtained not a few specimens and much information (like many other visitors of that early period), which, however, he never acknowledged.
As it may be of some little interest I will just quote what I then wrote about that larva and imago, in a letter to Sir W. Hooker, dated "July, 1841," and published by him in the London Journal of Botany (1842), vol. I., pp. 304, 305.
"In a phial you will find specimens of what I believe to be the true larvæ of Sphæria robertsii.[3] These larvae are abundant in their season on the foliage of Batatas edulis (?)[4], the kumara of the New Zealanders; to the great distress of the natives, who cultivate this root as a main article of their food, and whose occupation, at such times, is to collect and destroy them, which they do in great numbers. They vary a little in colour, as may be observed in the specimens sent. The New Zealanders call them Hotete and Anuhe (the same names which they apply to the Sphæria robertsii itself), and always speak of them as identical with that Fungus. The common belief is, that both (those living on the kumara and those which bear the Fungi) alike descend from the clouds! this opinion doubtless arising from their sudden appearance and countless numbers.
"A moth from the larvæ also accompanies the above, for I have fully satisfied myself of their identity. In 1836 I kept the larvæ under glasses, and fed them with the leaves of kumara (much to the annoyance of the natives), until the perfect insect was produced. There cannot reasonably exist a doubt that this insect deposits or drops some of her eggs on the branches of the raataa (Metrosideros robusta, A.C.), beneath which tree alone the Sphæria robertsii has hitherto been found, when they (the larvæ) fall to the earth beneath, die, and the Sphæria is produced.
"I think I can offer a fact for consideration relative to their being only (or chiefly) found beneath Metrosideros robusta. One fine evening last summer, when enjoying, as usual, a promenade in my garden, just as the sun had set, I was admiring the splendour of some plants of Mirabilis, which had just unfolded their scarlet petals. Suddenly several of these moths made their appearance, darting about the plants in every direction, pursuing one another, and eagerly striving to obtain the honey which lay at the bottom of the perianths of the Mirabilis. From this plant they flew upwards to the flowers of a stately Agave (A. americana), where, being joined by other moths, their congeners, their numbers soon increased; and thus they continued to enjoy themselves every evening during the whole season. The inference I deduce is this, that the M. robusta, blooming at this season, having scarlet flowers which abound in honey, becomes the centre of attraction of these insects—increased, too, by its densely crowded coma of inflorescence, more particularly so from the blossoms being always at the extremity of its branches; by which, and by their colour, this tree may at once be distinguished from the other denizens of the forest, even at a great distance.
"The larva whereon the Sphæria is found, when first taken out of the earth, is white internally, and appears solid and succulent. A finely-cut slice, when held against the light, presents a beautiful appearance."
I may further add that, 25–30 years back, I had a honeysuckle (Lonicera periclymenum) trained round the doorway of a house in my garden. This plant flowered abundantly in the summer, and it was interesting and curious of an evening to sit on the step (as I have often done) and watch those large moths (Hepialus); they would visit the plant in great numbers, and unrolling their long probosces, probe the flowers to get at the honey, passing quickly from flower to flower, and continually coiling and uncoiling their long trunks with great rapidity; they never lighted on the plant, and all the time kept up a tolerably loud humming noise from the quick and incessant vibrations of their wings, which, indeed, drew the attention of the cats, who often, in consequence, captured them.
- ↑ I may here mention that the moth described in Dr. Dieffenbach's work on New Zealand, Vol. II., p. 284, (Hepialus) was also raised by me from larvæ which I had fed on kumara leaves, much to the annoyance of the Maoris in those times, who made a great fuss and objection to my so doing. (See note at end.)
- ↑ In Spéciès Général des Lépidoptères Nocturnes.
- ↑ Cordiceps robertsii.—Hand-Book, Fl. N.Z.
- ↑ Ipomæa chryssorhiza.—Hand-Book, Fl. N.Z.