Art. XVIII.—Lepidoptera of Mount Ida.
[Read before the Wellington Philosophical Society, 25th September, 1900.]
The mountain-range that runs inland from the coast south of Oamaru, and loses itself in the broken country behind Mount St. Bathans, attains its highest altitude in Mount Ida (5,600 ft.). Situated as it is in the heart of the dry belt, the insect fauna of this mountain is extremely meagre, but withal exhibits some peculiar features, not the least interesting of which is the rapid and complete succession of species throughout the summer, more especially in the Lepidoptera.
On the shingle slopes near the summit Erebia pluto, the black mountain butterfly, is common enough, and, with swarms of Argyrophenga antipodum, lends an interest to the otherwise dreary prospect of tussock and shingle. No “Society for the Preservation of Butterflies” is needed to save these two hardy little species from extinction; they are secure in the possession of country that laughs to scorn the improving settler.
Between 3,000 ft. and 4,000 ft. Notoreas insignis occurs in March and April in abundance; it is particularly attached to a species of Raoulia. Except a few “micros.” and a single Dasyuris hectori, I have seen no other moths on the higher parts of the range.
On the lower half, however, between 2,000 ft. and 3,500 ft., many species occur. Swarms of Crambidæ are out on every hot day, and, of the twenty species that I took last summer, no particular one had exclusive possession of the field, as is so often the case in other parts of the colony. Crambus corruptus may be excepted, but only in the very early spring. Of the rarer Crambidæ, I have taken Thinasotia claviferella commonly in March amongst sedge, while Crambus flexuosellus is a rarity represented by one specimen. On the Maniototo Plains, 1,000 ft. lower, flexuosellus is common enough. Chrysophanus boldenarum and Lythria euclidiata occur all through the summer in swarms, as well as a duller Geometrid, apparently new, which has the same habits as euclidiata.
The succession of species in the Geometridæ is somewhat marked on the lower levels, though not so noticeable as with the Noctuidæ. Theoxena scissaria shows first; indeed, my
first specimen was taken at light while the snow was lying on the ground. I have seen none after August, but its habits in Canterbury appear to be different. Hybernated individuals of Xanthorhoe semifissata begin to show up in September, and with them the common Xanthorhoe bulbulata, which keeps on in undiminished numbers until Christmas, and then takes a back seat, though never disappearing. Xanthorhoe cineraria appears in October and November; and a week's hot weather in December is sure to bring out X. orophylla and Notoreas brephos in force. Xanthorhoe clarata appears in February (two months later than near the coast), and the last to show themselves are Hybernia indocilis and Xanthorhoe semifissata, both being attached to Discaria toumatou.
But it is with the Noctuidæ that the succession of species is the most striking. Leucania acontistis, one of the earliest, disappears completely after September, to be replaced by swarms of Leucania griseipennis, which prevails through November, but after Christmas is no longer to be seen. Leucania unica, propria, and Melanchra lithias hold the field each for a short time during January and February, but are generally extinguished after a night or two by M. mutans.
Such species as Leucania nullifera (the yellow form), L. atristriga, Melanchra composita, rubescens, phricias, and ustistriga come to light only in singles, and Orthosia comma occurs, but not commonly, throughout the summer. Amongst the rarities taken were Miselia pessota and Bityla defigurata. Of Heliolhis armigera, Plusia chalcites, and Agrotis ypsilon not a single specimen was seen.
The Coleoptera of the district are strongest in Otiorhynchidæ, the various species of which occur in plenty. With the exception of two large species of Inophlæus, none of the kinds are represented in my collection by less than twenty specimens. The species of the genus Nicæana are especially abundant, living as a rule in the patch plants on the shingle flats, and, as usual in a dominant genus, variation is rampant. The sexes also differ considerably, so that the list of established species must be severely revised.
In striking contrast to the Dunedin district, from which such a long list of Pterostichi have been recorded, only four species have turned up, ovatellus and fultoni being the commonest.
Our largest necrophagous beetle, Necrophilus prolongatus, attends to the waste products of the rabbit trade. Although only known from New Zealand, so far as I am aware, this species, like Metriorhynchus and a few others, is so unlike the general type of our fauna as to suggest naturalisation.