Part 15

The perfect insect appears from November till January. It was formerly a common species near Rakaia, but is now much scarcer.

MELANCHRA PARACAUSTA, Meyr.

(Mamestra paracausta, Meyr., Trans. N. Z. Inst. xix. 15.)

(Plate IV., fig. 28 , 28A .)

This species has occurred in the South Island at Mount Arthur, Castle Hill, and Invercargill.

The expansion of the wings is about 1-3/8 inches. The fore-wings are dull white with an irregular, central, longitudinal, blackish-brown streak becoming very broad towards the termen; there is an oval reddish-brown blotch near the base, but no distinct transverse lines; two conspicuous elliptic, white marks are situated on the termen near the tornus. The hind-wings are pale grey, with an obscure central shade and a series of brownish dots along the termen.

The species appears somewhat variable. In some male specimens the white colouring is largely replaced by pale yellowish-brown. Described and figured from specimens in the collections of Messrs. Fereday, Hawthorne, and Philpott.

{16}MELANCHRA INSIGNIS, Walk.

(Euplexia insignis, Walk., Suppl. 724. Xylina turbida, ib. 754. Mamestra polychroa, Meyr., Trans. N. Z. Inst. xix. 16. Mamestra insignis, Meyr., ib. xx. 45.)

(Plate IV., fig. 29 , 30 .)

This pretty species has occurred at Palmerston and Wellington in the North Island, and at Blenheim, Christchurch, and West Plains near Invercargill in the South Island. It is probably common and generally distributed.

The expansion of the wings is about 1-3/8 inches. The fore-wings are pinkish-brown; there is a short black streak near the centre of the wing at the base, and an irregular, extensive black marking along the dorsum; the orbicular, reniform, and claviform spots are large, margined first with green and then with black; a fine white line is situated parallel with the termen, edged with green, and emitting two sharp tooth-like markings; beyond this line the ground colour of the wing is dark-brownish-black. The hind-wings are dull brown, darker towards termen; the cilia are white with a brown line. The antennæ of the male are slightly bipectinated. In the female the ground colour is considerably paler, the black markings much darker, and more suffused, and the posterior half of the reniform is usually creamy-white.

Some specimens have the green and black markings slightly more pronounced, but otherwise there are no important variations.

The eggs are deposited in October and November. When first laid they are pale greenish-white, but become dark brown in the centre as the enclosed embryo develops. The young larvæ emerge in about a fortnight. At this time the two anterior pairs of prolegs are very short, causing the caterpillar to loop up its back when walking. In colour the young larva is pale brown, with numerous black warts emitting several long, stiff bristles. It is very active, and busily devours the soft green portions of the dock leaves, leaving the harder membrane untouched. Twelve days later the larva becomes pale green in colour, and moults for the first time, after which traces of subdorsal and lateral lines present themselves. Growth then proceeds with great rapidity, and in another eleven days the larva again sheds its skin. The last moult occurs a fortnight later.

At this time the larva is pale greenish-brown, inclining to yellow on the ventral surface. The lateral lines consist of a series of black markings near the posterior margin of each segment; the subdorsal lines are represented by four oblique black marks on each side of the four posterior segments of the larva. The region between these lines is much clouded with yellowish-green or pink, the larvæ having a tendency to diverge into pink and green varieties. The anal segment is dull yellow. The head is brown, with two black stripes and several black dots.

Whilst rearing these larvæ I noticed that during the daytime they invariably hid themselves under the blotting paper at the bottom of the breeding cage. No doubt, under natural conditions, they retreat beneath the ground, only coming abroad at night to feed. This habit would account for the difficulty experienced in finding larvæ of this genus in a state of nature.

The pupa state is spent in the earth, and occupies about a month.

The moth appears towards the end of January. It evidently hibernates through the winter, as it is often seen very late in the autumn, and is always one of the first moths to come to sugar in the early spring. It is frequently observed at rest on fences and trees in the daytime.

{17}MELANCHRA MAYA, n. sp.

(Plate IV., fig. 31.)

A single specimen of this species was taken on the Tableland of Mount Arthur, at an altitude of about 3,500 feet.

The expansion of the wings is 1-5/8 inches. The fore-wings are bright yellowish-brown, paler towards the apex; there are two broad, shaded, black stripes at the base, one near the middle edged with yellow above, and one below the middle edged with yellow beneath; the orbicular is oval, oblique, edged with black except towards the costa; the claviform is rather irregular, dark purplish-brown; the reniform is very large, dark purplish-brown edged with black; there is a large elongate patch of very dark brown at the tornus, partly edged first with yellow and then with black; another smaller patch is situated on the termen near the middle, bisected by a fine yellow line. The hind-wings are grey; the cilia of all the wings are yellowish-brown. The head and thorax are purplish-brown, the abdomen dull brownish-grey.

MELANCHRA PLENA, Walk.

(Erana plena, Walk., Suppl. 744. Mamestra sphagnea, Feld., Reis. Nov., pl. cix. 17. Dianthoecia viridis, Butl., Cist. Ent. ii. 547. Mamestra plena, Meyr., Trans. N. Z. Inst. xix. 17.)

(Plate IV., fig. 32.)

Apparently common in the Canterbury district, where it has been taken at Christchurch and Mount Hutt. In the North Island it has occurred in the neighbourhood of Wellington.

It resembles Melanchra insignis in every respect except that the head, thorax, and fore-wings are entirely suffused with green; there is no central black streak at the base, and the orbicular, reniform, and claviform spots are smaller.

It varies a little in the intensity of the green colouring.