Genus 1.—ARGYROPHENGA.
Eyes glabrous. Club of antennæ somewhat abrupt. Fore-wings with lower margin of cell greatly dilated towards base; veins 8, 9, 10, and 11 out of 7; vein 12 greatly dilated towards base.
Of this genus there is one species in New Zealand.
ARGYROPHENGA ANTIPODUM, Doubleday.
(Argyrophenga antipodum, Doubleday, Ann. and Mag. Nat. Hist. xvi. p. 307 (1845); Gen. Diurn. Lepid. pl. 63, fig. 6 (1851); Butler, Erebus and Terror Lep., pl. 8, figs. 4, 7 (1874).)
(Plate [XI]., fig. 4 ♂, 5 ♀, 3 variety, 6 under side of ♂, 7 under side of variety; Plate [III]., fig. 4 larva, fig. 29 pupa.)
This species occurs commonly on the tussock lands from Christchurch to Invercargill. In the provinces of Nelson and Marlborough it is, I believe, confined to situations having elevations of from 2,000 to 4,000 feet above the sea-level. It has never been captured in the North Island.
The expansion of the wings varies from 1⅜ to 1¾ inches. Above, all the wings are dull brownish-black, paler near the body; the outer portion of each is covered with a large patch of bright orange-brown (northern form), or fawn colour (southern form); on the fore-wings this patch contains a large oval black spot, with two white dots in the middle; on the hind-wings there are two, three, or four black spots, with one white dot in the centre of each; beneath, the markings on the fore-wings resemble those of the upper surface, except that there are often several short silvery stripes near the apex; the hind-wings are dull yellow, with silver streaks between the veins, and one broader streak in the centre of the wing. The female is much paler than the male, with the borders of the wings whitish.
This insect is extremely variable. The colouring appears to be much influenced by local conditions. On the Dun Mountain, Nelson district, at an elevation of about 2,700 feet, a very small light form occurs in which the sexes are almost exactly alike. There are only two perfect spots on the upper surface of the hind-wings; the other spot is rudimentary, and has no white central dot. On the under side there are no silver stripes near the apex of the fore-wings, and only five or six silver stripes on the marginal portions of the hind-wings (see Plate [XI]., figs. 3 and 7). At Kekerangu, on the "Chalk Range," at an elevation of from 3,000 to 4,000 feet, a similar but slightly larger form occurs. On the Tableland of Mount Arthur, Nelson district, 3,600 to 4,600 feet above the sea-level, the females are paler than in either of the preceding forms, and the males darker, so that the sexes are well marked; but there are no silvery stripes on the under side of the apex of the fore-wings, and usually only five stripes on the marginal portions of the hind-wings. Finally, in the Canterbury, Otago and Southland butterflies (southern form), we have the large, very dark reddish-brown coloured male insect with large ocelli, and the extremely pale yellow female with small ocelli, the two sexes here exhibiting the greatest differentiation. On the under side, the male has several small silver stripes near the apex of the fore-wings, and seven stripes on the marginal portions of the hind-wings. (See Plate [XI]., figs. 4, 5, and 6.) In elevated situations in Canterbury, however, I have taken a somewhat similar variety to that found on the Mount Arthur Tableland. I have also taken similar forms on Mount Robert near Lake Rotoiti, Nelson district, these having, in addition, numerous white hairs on the wings near the body.
Besides these extreme variations, which appear to be largely dependent on local conditions, great variability exists with respect to the number and size of the ocelli or white-centred spots. In some specimens there are no ocelli on the hind-wings; in others, two, three, or four very minute ones, whilst others have all four very large. Occasionally specimens have a minute ocellus below the large one on the fore-wings. Were it not for the intermediate varieties, there would probably be little hesitation in separating the extreme forms of this insect into several distinct species; but as they are connected by a host of intermediate forms, it is quite impossible even to divide them into varieties.