Arctesthes titanica Patrick, Patrick & Hoare

Patrick, Brian H., Patrick, Hamish J. H. & Hoare, Robert J. B., 2019, Review of the endemic New Zealand genus Arctesthes Meyrick (Lepidoptera, Geometridae, Larentiinae), with descriptions of two new range-restricted species, Alpine Entomology 3, pp. 121-136 : 121

Arctesthes titanica Patrick, Patrick & Hoare sp. nov. Figs 9-11, 16, 26, 27, 32, 35 (map)

Type material.

Holotype: male (pinned), 'NZ OL 800m White Burn Sth Br Von R 4 Feb 2006 B M Lyford / NZAC slide Geo. 29 genitalia ♂' [South branch of Von River: 45°13'S, 168°21'E] (NZAC). Paratypes (1 male, 2 females): 1 male, same locality as holotype, 6 Mar 2004, B. & H. Patrick (NZAC) (Figs 9, 16); 1 female, same data as holotype but not dissected (Fig. 10) (NZAC); 1 female, same locality as holotype, 18 Feb 2004, S. Morris (genitalia on slide NZAC Geo. 32) (NZAC).

Other material examined.

3 males, 3 females, same locality as holotype, 6 Mar 2004, B. & H. Patrick; 4 females, same data as holotype but not dissected; 1 female, OL: North Branch of Von River, 18 Feb 2006, B.M. Lyford; 3 females, North Branch of Von River, 17-18 Feb 2007, B.H. Patrick (Fig. 11). (NZAC, BLNZ, BPNZ).

Diagnosis.

This species can easily be distinguished from A. catapyrrha by its larger size (in spite of the slight overlap in wingspan measurements, this is always a much more robust, larger-winged moth) and the almost unmarked hindwing upperside. The strongly 3-lobed antemedian line on the hindwing underside is also diagnostic. Differences from A. avatar are given under that species, below.

Description.

Adult male (Figs 9, 16): Wingspan 21-22 mm. Male antennal pectinations up to ca 4 × flagellum width. Labial palpi without hairlike scales projecting laterally, with moderately long, dark grey hairlike scales ventrally. Head and thorax blackish with admixture of scattered white to silvery grey scales; strip of pure white scales along antero-ventral margin of eye. Forewing ground colour (areas between transverse markings) mid-grey, suffused with pale ochreous brown in basal blotch, central fascia and along veins distally (brown colour appears darker when not seen under magnification); proximal line pale grey mixed pale brown, with slight convex curve towards costa; antemedian line pale grey mixed pale brown, rather strongly V-shaped centrally; discal dot black, closer to antemedian than to postmedian line; central fascia usually mid- grey in central band around discal dot, black, strongly suffused pale brown exteriorly; postmedian line pale brown mixed pale grey, strongly sinuous, with large V- to U-shaped evagination centrally, section between evagination and costa weakly to strongly convex; veins lined blackish and speckled pale brown beyond discal cell; distal line pale grey, rather indistinct; fringe dark grey, weakly chequered blackish. Hindwing ground colour bright orange; basal blotch suffused blackish except in narrow strip along costa, the suffusion extending along anal margin of wing to anal angle; antemedian line represented only by variable short dark section adjacent to anal margin, but pallid, more or less W-shaped underside fascia beyond antemedian showing faintly through in normal light (not or barely visible in strong overhead light); postmedian line obsolete, except for slight smudge on anal margin; terminal line obsolete, but series of black dashes along termen very distinct; fringe blackish, distally with some brownish white scale-tips. Forewing underside (Fig. 16) pale orange; antemedian line absent or present only as dark smudge on costa; discal dot small, distinct, black; postmedian line distinct only in costal 1/3 of wing or less, blackish, double, with upper part of strong median evagination usually still represented where lines fade, sometimes suffused brownish between the two lines; outer line more or less distinctly edged white towards costa; subterminal fascia represented by series of brown elongate smudges between veins in costal 1/3 of wing; terminal fascia distinct, brown, narrowing and petering out towards tornus; a series of dark dashes along termen. Hindwing underside pale ochreous brown; basal blotch with scattered whitish scales, distal end of blotch a dark brown line, roughly following contours of antemedian line; antemedian line strongly 3-lobed, with third lobe cut off by anal margin of wing, invagination between first and second lobes incorporating distinct elongate discal spot; a very distinct white fascia beyond antemedian line, following its contours; weakly defined postmedian line beyond fascia, blurred distally into broad brown distal area, which is bisected by whitish scalloped subterminal line. Abdomen blackish, sprinkled pale brown, distal margin of each segment narrowly white; anal tuft blackish, with some scales tipped brownish white.

Male abdomen and genitalia (Figs 26, 27): S3-4 and 6 elongate (subrectangular), S5 more squarish, all sternites evenly sclerotised; T2-6 evenly sclerotised. Uncus digitate, narrow, attenuate and minutely hooked apically; labides very large, robust, strongly C-shaped, blunt apically; dorsal scobinate portion of manica with rather numerous sharp teeth; juxta flat, broad, tongue-shaped, with rounded blunt apex; valva moderately short, rather narrow, with rounded apex; basal costal sclerite with central process distinctly projecting beyond valval costa, (apex of sclerite bluntly rounded); sacculus process very large, C-shaped, projecting well beyond valval costa and apex reaching just beyond valval apex, dorsally and apically with dense fine spinules; saccus moderately short, very weakly 3-pointed, hardly recurved under genital capsule. Phallus without distinct tongue-like apical process; vesica scobinate, with two symmetrical cornutal patches, each containing numerous rather long, curved spine-like cornuti.

Adult female (Figs 10, 11): Wingspan 19-22 mm. Similar to male, but antennae without pectinations; labial palpi with ventral scales mostly brownish white; forewing ground colour distinctly paler than in male, with central fascia more strongly contrasting; forewing fringe distinctly chequered dark and pale.

Female genitalia (Fig. 32): Total length ca 2.4 mm. Ovipositor lobes subtriangular, apically moderately blunt. S8 with lamella postvaginalis broad, smooth and flat, lacking concavity. Ostium very broad; antrum a squat, broad sclerotised chamber weakly differentiated from posterior portion of ductus bursae; ductus bursae thickly membranous, not distinctly rugose, short and broad. Corpus bursae membranous, round.

Distribution.

(Fig. 35). At present only known from two localities in the valley of the Von River, south of Lake Wakatipu, Otago Lakes.

OL.

Biology.

The species is only known from intermontane wetlands. Both the north and south branches of the Von River harbour rather extensive valley floor wetlands that are a mixture of cushion and moss bogs at 800-820m, surrounded by short tussock or copper tussock ( Chionochloa rubra subsp. cuprea) grasslands; individual wetlands are approximately 0.1-0.4 ha in extent. The cushion plant Oreobolus pectinatus is the dominant cushion species, but a wide range of grasses, herbs and sedges share this habitat. Adult moths have been found on four occasions between 4 February and 6 March, but as they were relatively numerous each time and in good condition, their flight period probably extends from late January to late March at least. Adult females laid yellow eggs on leaves which hatched 13 days later. Larvae were given a variety of exotic and native herbs to feed on of which Plantago , prostrate-growing Coprosma , Ranunculus , Bellis and Trifolium were eaten; however, rearing was unsuccessful. The first instar larvae are brown-grey in colour and quite active. Unfortunately, no photographs were taken of the larvae.

Etymology.

Based on its large wingspan compared to A. siris and A. catapyrrha , the species is named (with an element of hyperbole) after the Titans of Greek mythology, primeval deities of enormous size and strength, and by extension after the legendary but ill-fated ‘Titanic’, in its time the largest passenger ship ever built and the subject of the popular James Cameron movie of 1997 (see also Etymology under A. avatar below). The name is a Latin adjective.

Remarks.

Given the narrow distribution of this species and the fragility of its wetland habitat in an area still managed for extensive pastoralism, this species is threatened with extinction. Although the moth is relatively abundant where it occurs, the habitat is small and vulnerable to damage from farming practices such as over-sowing, grazing, stock trampling and vehicle damage. Additionally the areas are mostly unfenced, so recreational vehicles have access to these wetlands and could easily inflict damage as has occurred elsewhere in Otago and Southland.