The New Zealand Swift Moth

Dominion, Volume 27, Issue 17, 14 October 1933, Page 20

The New Zealand Swift Moth

(By

J. Drummond, F.L.S., F.Z.S.,

~ for “The Domnion.’’)

vw nr ANT swift moths sent for identification during the past six weeks /I iire evi(l( -‘ nce that tllis species, Hepialus virescens, is unusually ’%/ I plentiful in the North Island at present. All the individuals \ v i sent were caught in the North Island, which is particularly

favoured by the species. It is found in the South Island, but not us often as in the North. Only occasionally is it seen in or near Chris'church. In “The Butterflies and Moths of New Zealand,” Mr. G. V. Hudson gives its season as from early in September to the middle of November. It is a creature of the spring rather than of the summer. As it is nocturnal, •it doubtless is more plentiful than might be believed. Like the proverbial foolish moth, it is fascinated by lights. It. often flutters into well-lighted shops and dwellings. The males alone, as a fule, fall under this fascination. Less susceptible to gay lights, the females are not lured to destruction so often. Amongst correspondents who have noted the species recently are a resident of Carter's Flat, Cambridge, Mr. H. Hobart, Waitoa, and Mr. O. C. Pleasants, Matiere. Mr. Pleasants's specimen was caught in tea-tree scrub. Many members of the species may live by day amongst tea-tree, or in native forests, without being seen, their costumes protecting them by harmon ising with their environment.

New Zealand’s swift moth is called the swift moth because member:of its family in the Old Country are called swift moths. The family. Hepialidae, a primitive type, has representatives in most parts of the world. New Zealand lias no fewer than twenty species. All except the species now considered belong to one genus, Borina. Most of these, in their caterpillar stage, are attacked by a species of fungus, which converts the living caterpillars into the vegetable caterpillars that always cause wonder. The United Kingdom has only five species in the family. Individuals of these species are small and inconspicuous, compared with New Zealand’s swift moth. The whole of Europe has only nine species. % Specimens sent or described show that individuals vary in colours awl markings. The large size of a New Zealand swift moth gives it prominence in this Dominion’s Insect life. Tn a general way, the fore-wings may be described as green or yellow. They may be bluish-green or yellowish-green, light green or vivid green. Not Infrequently, they bear irregular black or

white marks. In view of the swift moth's variable colours, Mr. Hudson’s description, which may be accepted as official, is given as follows: —“The male has a wing expansion of four inches. The male's fore-wings are bright green, with a series of paler ring-shaped markings between the veins. An irregular row of white spots crosses the wing near the middle. There is a small white spot on the front, margin near the base. The male’s hind-wings are very pale yellowish-brown near the body. In the middle, they are pure white, and on the outer margin they are pale green. The male’s head and thorax are green Its abdomen is white, tinged with green at the tip. The female is larger, with a wing expansion sometimes of six inches. Its wings are more attenuated in shape than the male's. Its fore-wings are green, mottled with black. Its hind-wings are pale reddish-brown, becoming green at the tip. ’ In spite of the variable characters of individuals, this should enable anybody to identify a swift moth.

With Mr. Hudson's permission, the temptation to quote further from his valuable book, the product of observations extending over about forty years, may be gratified. A female swift moth, he states, lays about 2000 small, round, yellowish eggs. As they are deposited indiscriminately, a cater pillar, on bursting out of the shell, must find its way along the ground to the stems of a food-plant. As many perish before they reach a plant, the females' great fecundity, apparently, provides against heavy mortality in early life The caterpillars tunnel the stems of shrubs and trees. The eat the wood, biting into it with their powerful mandibles. Fully grown, a caterpillar is from two inches and a half to three inches long, dull yellow, and has a. large, dark brown head. The puriri tree is one of the favourite food-plants, and the swift moth caterpillar sometimes is called the puriri grub. A complete tunnel is an elaborate piece of engineering. In the floor of a horizontal section, running along a branch or a stem, there is a silken lid for all the world like a top trap-door made by human hands. If it is raised there is disclosed a long, dark, perpendicular .shaft, half an inch in diameter, with a sheer drop of six inches. The trap-door seems to be intended to keep enemies out of the lower shaft. Many spiders, slugs, woodlice and other creatures are found In the upper tunnel. The trap-doors prevent them from going below and attacking the caterpillars in their homes.