(Papilio archippus, Fabricius, Spec. Ins., p. 55, n. 243 (1781). Danais archippus, Butler, Butterflies of N. Z., Trans. N. Z. Inst. x. 265. Anosia plexippus, L.)
(Plate [XI]., fig. 1, fig. 2 under side; Plate [III]., fig. 3 larva, fig. 27 pupa.)
This handsome insect has occurred from time to time at various localities in both the North and the South Islands, but does not appear to be generally common. Particulars of the early captures of this butterfly are thus given by Mr. Enys[[44]]: "First recorded as a New Zealand insect by Mr. Fereday, in a paper read before the Canterbury Institute, January 2, 1874, and printed in vol. vi. of 'Transactions.' Mr. Fereday received the butterfly from F. H. Meinertzhagen, of Hawkes Bay. Dr. Hector also obtained it in Westland. It has also been caught near Auckland. In vol. xi. of 'Transactions' Mr. F. W. Sturm records that he first saw this insect, or a closely allied one, at the Reinga, up the Wairoa River, Hawkes Bay, December, 1840, or January, 1841. In 1848 he captured a number at the Waiau, a tributary to that river. Again in 1861 he captured three on the Rangitikei River near Mr. Birch's run. He also records other captures." From these records it will be seen that the insect was observed as early as 1840, and it thus seems scarcely probable that it was accidentally introduced by man, as Mr. Butler appears to suppose.[[45]] Recently A. erippus has occurred many times in the neighbourhood of Cook's Straits. In 1879 several specimens were bred from larvæ found by Mr. C. W. Lee near Wangaehu. In 1881 I captured two specimens near Nelson and saw three others. In 1890 two specimens were taken by Mr. R. I. Kingsley, and in January of the following year I captured two more, all near Nelson. During the autumn of 1892 one specimen was taken near Otaki by Mr. Rutherfurd, and several others were seen. The same year a specimen was also taken by Sir James Hector at Petone. In 1896, I understand from Mr. Kingsley, several specimens were again seen in the Nelson district.
The expansion of the wings is from 3¾ to 4¼ inches. Above, all the wings are rich orange-brown bordered with black, the veins are also black. There are two rows of small white spots round the margins of all the wings, and several orange-brown spots near the apex of the fore-wings. Beneath, the markings are similar, except that the white spots are larger, and the hind-wings are very pale yellowish-brown. The male has a black chitinous spot on vein 2 of the hind-wings which is wanting in the female; the wing-veins in the male are also slightly narrower.
The larva of this insect feeds on most of the different kinds of milkweed (Asclepias), and also upon dogbane (Apocynum). A single caterpillar, fully grown, which was found in a building in the centre of the town of Wellington, formed the subject from which the figures of the metamorphosis of this insect were taken, but this specimen did not afford sufficient material for an exhaustive investigation of the life-history. The following account, taken from Professor Riley's 'Third Annual Report of the Noxious, Beneficial, and other Insects of the State of Missouri,' is therefore inserted:—
"The egg is invariably deposited on the under side of a leaf, and is conical and delicately reticulate with longitudinal ribs, and fine transverse striæ. It is yellowish when first deposited, but becomes grey as the embryo within develops.
"In about five days after laying the egg hatches, and the young larva as soon as hatched usually turns round and devours its egg-shell—a custom very prevalent with young caterpillars. At this stage it differs considerably from the mature larva; it is perfectly cylindrical, about 0·12 inch long, and of much the same thickness throughout. The head is jet black and polished; the colour of the body is pale greenish-white, with the anterior and posterior horns showing as mere black conical joints, and with two transverse-oval black warts, nearer together, on the first joint. It is covered with minute black bristles, arising from still more minute warts.
"When the young larva is three or four days old a dusky band appears across the middle of each joint, and by the fifth or sixth day it spins a carpet of silk upon the leaf, and prepares for its first moult. After the first moult the anterior horns are as long as the thoracic legs, the posterior ones being somewhat shorter; the characteristic black stripes show quite distinctly, but the white and yellow stripes more faintly. After this it undergoes but slight change in appearance, except that the colours become brighter, and that at each successive moult the horns become relatively longer. There are but three moults, and the intervals between them are short, as the larvæ frequently acquire their full growth within three weeks from hatching.
"As soon as the larva is full grown it spins a little tuft of silk to the under side of whatever object it may be resting upon, and after entangling the hooks of its hind legs in the silk it lets go the hold of its other legs and hangs down, with the head and anterior joints of the body curved. In this position it hangs for about twenty-four hours, during which the fluids of the body naturally gravitate towards the upturned joints, until the latter become so swollen that at last, by a little effort on the part of the larva, the skin bursts along the back behind the head. Through the rent thus made the anterior portion of the pupa is protruded, and by constant stretching and contracting the larval skin is slipped and crowded backwards until there is but a small shrivelled mass gathered around the tail. Now comes the critical period—the culminating point.
"The soft and supple chrysalis, yet showing the elongate larval form with distinct traces of its prolegs, hangs heavily from the shrunken skin. From this skin it is to be extricated and firmly attached to the silk outside. It has neither legs nor arms, and we should suppose that it would inevitably fall while endeavouring to accomplish this object. But the task is performed with the utmost surety, though appearing so perilous to us. The supple and contractile joints of the abdomen are made to subserve the purpose of legs, and by suddenly grasping the shrunken larval skin between the folds of two of these joints as with a pair of pincers, the chrysalis disengages the tip of its body and hangs for a moment suspended. Then with a few earnest, vigorous, jerking movements it succeeds in sticking the horny point of its tail into the silk, and firmly fastening it by means of a rasp of minute claws with which that point is furnished. Sometimes severe effort is needed before the point is properly fastened, and the chrysalis frequently has to climb by stretching the two joints above those by which it is suspended, and clinging hold of the shrivelled skin further up. The moment the point is fastened the chrysalis commences, by a series of violent jerkings and whirlings, to dislodge the larval skin, after which it rests from its efforts and gradually contracts and hardens. The really active work lasts but a few minutes, and the insect rarely fails to go through with it successfully. The chrysalis is a beautiful object, and as it hangs pendant from some old fence-board or from the under side of an Asclepias leaf, it reminds one of some large eardrop; but, though the jeweller could successfully imitate the form, he might well despair of ever producing the clear pale-green and the ivory-black and golden marks which so characterize it.