Biological Notes on New Zealand Lepidoptera.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 60, 1930, Page 259

Biological Notes on New Zealand Lepidoptera. By A. V. Chappell. [Communicated by Mr. A. Philpott; received by the Editor, 27th March, 1929; issued separately, 15th August, 1929.] 1. Life-history of Selidosema Modica. Egg.—Elliptical; olive-green to pale cinnamon, becoming very pinkish before hatching; laid in groups or in rows, each egg separate, on leaves and twigs, usually on the under-surfaces. Larva.—On hatching about one-eighth of an inch; very dark brown with broad, white, dorsal, subdorsal and lateral lines; head pale ochreous; ventral surface olive-green; the colouring throughout is in lines of uniform width; progresses rapidly with a series of beating movements. Dark brown tinged with black; broad silvery-white dorsal line; fine brownish-white subdorsal line; lower lateral surface ochreous-brown with a series of short, oblique whitish lines on the central and posterior segments; on the lateral surface the segmental divisions, particularly of central segments, are banded with black; head ochreous-brown; ventral surface dirty whitish with brown lines. Blackish-brown; broken dorsal line, whitish faintly tinged with pink on 2nd to 6th segments, fine and dark black on segments 7 to 9, lightish-brown on segments 10 to 12; alongside the dorsal line on segments 7 to 9 are several white spots and patches; the 5th and 6th segments are slightly marked on the lateral surface with lightish brown; head black; ventral surface, pale whitish brown; in places the whitish-brown merges slightly on to the lateral surface. Dark brown; finely pencilled with white; whitish dorsal line marked at intervals with black and tinged with pinkish on posterior segments; broken ochreous-brown lateral line; segmental divisions marked with bands of black; head ochreous-brown. Light brown; paler dorsal line, more clearly defined on the anterior segments, broken by pale brown and, at irregular intervals, by black marks; on the 5th to 11th segments the dorsal line widens into a series of diamonds each one from segments 5 to 9 marked with black; several fine ochreous-brown subdorsal and lateral lines; several series of small black spots; short fine hairs; head pale ochreous-brown; spiracles white finely ringed with black; skin of lateral surface very puckered; ventral surface, pale whitish-brown with fine white lines. Darkish-brown marked with paler brown; darker on lateral surface of posterior segments; slightly pencilled with black and white; dorsal line, whitish on segments 2 to 5, pale brown on 6 to 9, paler still on the 10th to 12th; on segments 5 to 11 the dorsal line broadens into a series of diamonds each one from 5th to 9th segments marked with black; fine ochreous-brown subdorsal line; head dark brown,

face whitish heavily speckled with dark brown; spiracles white finely ringed with black; short fine hairs; skin of lateral surface rather puckered; ventral surface pale whitish-brown finely pencilled with white and black. Mature Larva.—Length about 1 ⅛ inches; stone-grey mottled with lighter and darker shades; brownish on posterior margins of segments 5 to 9; dorsal line very pale grey faintly tinged with pinkish-white on segments 2 to 5 and with pinkish on 10th and 11th segments; on 5th to 11th segments the dorsal line widens into a series of diamonds, each one from segments 5 to 9 marked with black; dorsal series of small black spots; dirty whitish dorsal patch on the 12th segment; very fine, pale subdorsal line and a similar lateral line; hairs very short and fine; head small, dark grey, paler facially and marked with darker colour; spiracles white finely encircled with black; lateral series of small dark spots; skin very puckered on lateral surface; ventral surface, pale cinnamon marked with grey and black, two series of small black spots; 10 legs. Variations.—Some specimens light brown and some biscuit-brown; in these brown forms the dorsal line is usually white and unbroken and a black lateral line, fading beyond the anterior segments, is often present; in some the white pencilling is rather conspicuous. Protective coloration is good; the larva is usually found clinging to a dry bare twig and even in such a position is hard to detect, resembling as it does one of the small dry pieces of leaf or flower-spike so frequently remaining on the dead twigs of the foodplant. Habits.—Nocturnal; during day larva remains amid the foliage of the plant, usually clinging with curved or twisted body to a bare twig; eats semicircular nicks in the edges of the leaves; also eats the flowers; fairly active. Foodplant.—Hebe leiophylla. The above species of Hebe is the only one on which I have captured the larvae, but in captivity they feed readily on H. salicifolia and on various hybrid species. This is rather interesting, as at present S. modica has been taken only on the Lyttelton Hills, and according to Cheeseman Hebe leiophylla is not uncommon from Nelson to Otago. Cocoon.—Slight; spun amid sand and debris in breeding-box. Pupa.—Pale golden-brown to dark brown with the integument covering the wings slightly paler; female much stouter abdominally than the male. 2.Notes on the Flight of the Female, and on the Distribution of Selidosema Modica. Flight of Female. The wings of the female of Selidosema modica—particularly the fore-wings which have about the same area as the hind-wings—are very much reduced. The moth is undoubtedly in process of becoming apterous.

As is to be expected from the greatly reduced wing-area and the heavy abdomen, the powers of flight are very limited; the moth can do no more than flutter. On several occasions I have tested the flight of some of the females in a large room. Outside, of course, they would feel the effects of the gentle air-currents circulating among the bushes, but the aid to flight given by such currents would not, I think, be very great; indeed, they would be just as likely to hinder as to help. Hence a trial indoors may be taken as a very fair indication of the moth's capabilities. So far as my observations go, the moth cannot fly from a lower to a higher level. In order to reach a higher level it relies on the legs, aided by a beating of the wings, for locomotion. But taking off from a higher level it can flutter downwards in an irregular slant, at an angle varying from about 30 to 45 degrees. Now and again, in the course of the flight, the moth may rise a few inches, but it is enabled to do so only by the momentum gained earlier in the slant. The moth can run about very rapidly, and I think it more than likely that very often the wings are not used except as an aid in running. Even though they are used to this extent only it will, of course, be a very long time before the creature becomes apterous. Distribution of the Species. The range of the foodplant, Hebe leiophylla, extends, according to Cheeseman, from Nelson to Otago; moreover, it is fairly common on Banks Peninsula. But Selidosema modica is, so far as is known at present, restricted to the Lyttelton Hills. This restriction to such a very limited locality is undoubtedly the outcome of the dwindling of the bush on Banks Peninsula. It is probable that at one time the species ranged over a much larger area than it does now, though I do not think it ever ranged beyond this peninsula. It seems that the gradual loss of the power of flight took place after the moth had been driven back with the foodplant, through the dwindling of the bush, and then isolated in certain localities. The loss of the power of flight would be brought about partly by the isolation to small localities, and partly by the fact that the foodplant tends to be of social habits. Taking into consideration these two points, especially the latter, and the density of the top-growth of the N.Z. bush, it will be seen that the female moth would not need to depend on prolonged or sustained flight; it would only need to be able to progress easily over the thick foliage in search of the food-plant, and it could do this simply by fluttering. Hence the moth would not need to fly and would thus slowly but surely lose the power of flight. The encroachment of other growth among the Hebe would still further confine the moth to limited clumps of the foodplant. With the plentiful foliage of the Hebe the female would not need to range beyond the small clumps or colonies to deposit the eggs, and would thus advance yet a step farther towards the apterous state. Once the moth had to any extent lost the power of flight it would be impossible for it to pass over the larger gaps between the supplies of Hebe in the bush. And if in any locality the foodplant was wiped

out the moth would, in the event of the foodplant reappearing later, be unable to bridge the gap and would thus, through inability to regain lost ground, be still further isolated. Whereas the species might in time, and with great loss, succeed in passing from one colony or group of Hebe to another in the same bush, a bushless slope or valley would prove an insurmountable obstacle; it is as a direct result of long isolation and of this inability to regain lost ground that S. modica is restricted to such a limited locality on the Banks Peninsula. The species may be present on other portions of Banks Peninsula, but the process of isolation seems to have gone on to such an extent that it is now restricted solely to the Lyttelton Hills. 3. Notes on the Life-history of Scoparia Illota. The Mature Larva.—About 5/8 of an inch in length; pale brown with tinges of grey and pink; very fine indistinct dorsal line; dorsal, lateral and sublateral series of large, slightly raised, dark brown spots; numerous fine hairs; head dark golden-brown; 2nd segment slightly paler, edged with dark brown, horny dorsal plate; ventral surface slightly paler than the upper surfaces, a few small brown spots on some of the segments; 16 legs. Some specimens have a slight but distinct purplish tinge which is more noticeable when the larva is contracted. Habits.—Nocturnal; the larva mines the leaves of the foodplant, eating large galleries; enters leaf through a small hole in the under-surface; often fastens two or three leaves together and feeds in the shelter thus formed, in such cases it eats the under epidermis as well as the spongy tissue of the leaf; usually a flimsy silken gallery leading from the leaf or leaves upon which the larva is feeding into the moss and lichens which clothe the rock-faces on which the food-plant grows; the larva retreats along this gallery and spends the day in small shelter galleries constructed in the moss; the small golden-brown pellets of excrement lodge thickly in the silk of the galleries thus furnishing proof of recent or present occupation. Foodplant.—Cyclophorus (Polypodium) serpens. Cocoon.—Slight; usually spun amid debris of foodplant and moss on rock-face; sometimes spun between two or three of the leaves upon which the caterpillar has been feeding; the silk is whitish. Pupa.—Very shiny; thoracic portions dark brown, abdominal portions yellow-brown. 4. Notes on the Life-history of Hybernia Indocilis. Mature Larva.—Uniform light brown; slightly and finely pencilled with black, more particularly on the lateral surface; head small, slightly paler than the body, flat and heart-shaped facially; ventral surface slightly paler than the upper surfaces; 10 legs; the length is about 1 inch.

The colouring corresponds fairly closely to that of the older, stringy bark of the Lupin. Habits.—Nocturnal. Foodplants.—Lupin (Lupinus arboreus); Discaria toumatou. Pupa.—Dark reddish-brown tinged on thoracic portions with dark green; the green tinge gradually disappears. The above description of the larva was taken but two or three days before pupation. 5. Life-history of Leucania Purdii. Egg.—Globose, flattened above and below; light bluish-green; black with darker central spot on top; tawny; pale brown with darker spot; finely sculptured; laid in patches. Larva.—On hatching about 3 mm.; dirty white; blackish on anterior segments; very fine white dorsal line; reddish-brown lateral line; hairy; head large and pale ochreous. Pale dusky yellow slightly tinged with pale green; broad white-dorsal line; broad reddish-brown lateral line; head very pale yellow; segmental divisions whitish; ventral surface slightly paler than upper surfaces. Uniform pale dusky yellow; fairly broad, slightly darker, sub-dorsal line; black spiracles. Second to sixth segments become grey-green; remaining segments grey-green tinged with yellow, the yellow tinge increasing towards the anal segment; pale yellowish dorsal line and near this a series of faint dark spots; anterior segments finely speckled with brown; segments 2 to 5 bear large dark brown lateral patches which merge slightly into one another; on the same segments and immediately above the brown patches is a faint yellowish lateral line; head dark brown; spiracles, on anterior segments coral-red encircled with black, the others are black. Mature Larva.—1 ¾ to 2 inches long; heavily built; flattish anteriorly and posteriorly; dull grey-green finely speckled and splashed with brown on anterior segments and tinged and mottled with yellow on central and posterior segments; the 2nd to 5th segments bear large dark brown lateral patches merging slightly into one another; there are similar patches on the posterior segments and suggestions of them on the central ones; on segments 2 to 5 is a faint yellowish lateral line, fading gradually away, immediately above the brown patches; fine dorsal line and near this a slight speckling of brown; head large and dark brown; 2nd segment pale brown on dorsal surface; spiracles coral-red finely encircled with black, round each of those on the central and posterior segments the yellow tinge forms a darker patch; skin on lateral surface of posterior segments very puckered; ventral surface, pale yellowish-green; 16 legs; anal prolegs strongly developed; the skin throughout is rather transparent and the internal organs are traceable when the creature moves. Variations.—Some specimens tinged with light golden instead of yellow; others suffused with a rosy tinge; others again are entirely

and strongly suffused with lightish-brown or reddish-brown; some are ochreous pink with a darker pink dorsal line; the dark brown lateral patches vary in size and in depth of colouring. Habits.—Nocturnal; spends day well down in heart of foodplant, usually resting in cavity eaten in bases of young unrolled leaves; when disturbed drops and rolls up clasping the back of the head with the anal prolegs; rather sluggish; considerable gripping power; the young larva eats grooves in the epidermis of the leaves but the older larva eats right through the leaf; the larva not only eats in from the edges of the leaf but also eats through the central portions; prefers the young heart leaves. Foodplant.—Astelia grandis; in captivity the mature larva feeds readily on leaves of Cordyline australis. Cocoon.—Very little silk used; in captivity spun immediately below surface of soil or amid debris but usually a chamber was constructed in a hollow stick. Immediately before pupation many of the markings fade and larva assumes a light golden hue with a deep rosy tinge on the posterior segments. Pupa.—Deep wine colour; becomes almost black before the emergence of the moth; the thoracic portions are finely roughened; each abdominal segment is encircled at the anterior margin by a band, broader on the dorsal surface, of tiny pits.