Metura falcata Beaver 2020, sp. n.

Metura falcata sp. n.

(Figs 1 C–D, 3C–D, 4C–D, 5G, 6D)

Type specimen: Holotype ♂, AM.

Type locality: Lord Howe Island, unincorporated area of New South Wales, Australia.

Type material. HOLOTYPE, (in AM) ♂ Lord Howe Isl., Dec [as: xii] 1921, coll. Thompson / 14 / K45254 / Aust Mus no. K570250 / Dissection ID. EPB-020.

Additional material examined: 5 specimens, all larval bags: 4 in AM: 1 ♂ In tree, Neds Beach, Lord Howe Isl., 23 Feb 1988, H.J. & S. Disney / Aust Mus no. K570247. 1 ♀ as for previous except: Aust Mus no. K570246. 1 ♀ NSW: Roach Island, nr. Lord Howe Is, 31°30’07”S 159°04’06”E, 06 Feb 2001, S. Fellenberg / Aust Mus no. K515413. 1 ♀ as for previous except 09 Feb 2001 / Aust Mus no. K 507791. 1 in ANIC: North Beach Lord Howe Island NSW, 31.31S 159.03E, 6 Oct. 1979, E.D. Edwards.

Diagnosis. This new species is similar to the mainland Australian M. elongatus, but can be distinguished by a number of key characteristics of external and internal structure. The hindwing of M. falcata has the termen concave, with a more pointed apex than that of M. elongatus which has the apex less pointed, and the termen convex. Metura falcata further has the scales of the frons orange-yellow, which in M. elongatus are uniformly dark brown. The allopatric Metura aristocosma also has the frons yellow however that species is distinguished by the entirely black mesoscutum, which is yellow-orange in M. falcata. The pedicel of the antenna in M. falcata is clothed with piliform scales which are significantly paler compared with the other orange-yellow scales elsewhere on the body, whereas in M. elongatus the pedicel is the same orange-yellow colour as elsewhere. There are some differences in leg structure, the femur is ventrally convex distally and straight basally while in M. elongatus it is entirely convex. Foretibia dorsally concave, straight in M. elongatus, and the tibial spurs are larger and pointed in M. falcata. The male genitalia are similar only to M. elongatus however are distinctive, and differ particularly by way of the uncus shape, which is distinctly triangular with lateral margins straight in M. falcata but angular with apex more rounded in M. elongatus. Additionally, the vincular arms are convex at the inner margin of saccus, whereas they are parallel in M. elongatus. Transitellar arms are concave posteriorally, while the same structure is straight in M. elongatus. Ventral lobe of valva shorter in this new species, with sacculus less heavily spined, ground structure smoother, and more rounded than in M. elongatus. The phallus has the dorsal aspect of the vesica more than twice the length of ventral compared with M. elongatus which has this structure less than twice the length, and is broader in that species. The larval bag comprises of bare patches of silk adorned with stick sections and in this way is similar only to M. elongatus, from which it may be distinguished by the use of smaller, fewer twigs with greater expanses of bare silk in M. falcata, with the posterior ¼ of the bag bare of sticks or leaf material as often seen in M. elongatus.

Description. Male. (Figs 1 C–D, 3C–D) Forewing length incomplete, approximately 20 mm, hindwing 12 mm, expanse 43 mm.

Head. Scape trapezoidal, widest towards pedicel. Pedicel round, ¼ length of scape. Scape and pedicel covered in pale yellow piliform scales. Antennae bipectinate, filiform at apical flagellomere, yellow-ochreous scales along dorsal flagellomeres, setose, rami 5x width of flagellomere at widest point. Antennae incomplete, minimum 21 flagellomeres. Frons yellow-ochreous, Vertex yellow-ochreous.

Labial palps absent, labrum present.

Thorax. Dorsal patagium, tegula, anterior half of mesoscutum yellow-ochreous, posterior half black, mesoscutellum black. Ventral similar. Forelegs yellow-ochreous, tarsi and distal tibia black, mid- and hindlegs black. All lightly sclerotised when cleared (Fig. 5G), all tibiae with rounded node at ventral anterior apex. Foreleg with narrow elongate epiphysis, femur ventrally convex distally, straight basally. Foretibia dorsally concave. Mid and hindleg with two pointed tibial apical spurs. Forewing elongate, triangular; costa straight, gently convex toward apex, apex incomplete, termen convex medially, inner margin slightly concave posteriorly, convex anteriorly. Hindwing costa highly convex, apex pointed, termen concave, inner margin greatly expanded, convex, rounded where A1 meets margin. Both forewing and hindwing surface black, all veins weakly scaled, translucent. Underside as for above.

Abdomen. Dorsally black, interspersed with ochreous scales at posterior 1/4 rd and weakly between tergites. Ventral similar, yellow-ochreous from posterior ½. Sternite SVIII unknown (incomplete).

Genitalia. (Fig. 4 C–D). Saccus narrow, elongate, posterior margin narrow ‘V’ shaped. Vinculum with vincular arms convex at inner margin with saccus, outer margin at acute angle towards tegumen, more heavily sclerotised towards tegumen. Tegumen outer margin straight. Uncus broad, higher than wide, posterior apex triangular, bifurcate, weakly setose on dorsal aspect. Lateral margin straight. Transitellar arms sclerotised, anterior margin convex, posterior concave. Valvae elongate, apexes bifurcate to two lobes, ventral lobe shorter, hooked, short spines at apex, inner dorsal margin setose, sacculus moderately spined, rounded, smooth texture. Phallus elongate, ventrally concave, dorsally convex, ductus ejaculatorius heavily spined, vesica smooth, pronounced uneven mushroom-shape, dorsal aspect more than twice length of ventral.

Female. Unknown.

Larva. Unknown.

Larval Bag. Figure 6D. ♂ 80 mm length, 11 mm width, ♀ 96–116 mm length, 16–19 mm width. Silk light grey to whitish cream. Adorned with short sections of twigs and stems from larval food plant, attached irregularly with broad areas of bare silk between each adornment. Twigs utilised may vary between 2–10 mm long, longest twigs attached near to posterior apex, attached along entire length. Posterior apex bare of adornment.

Etymology. The specific epithet falcata refers to the sickle-shaped hindwing of the adult male, which has a falcate termen and apex. A noun in apposition.

Distribution. Figure 9A. Known only from coastal localities on Lorde Howe Island; from Neds Beach and North Beach, (main island) and nearby Roach Island.

Biology and phenology. The larval bags are all constructed with twigs and stem sections that closely resemble that of Melaleuca howeana Cheel (Myrtaceae), a common, dense shrub endemic to Lord Howe Island. A young specimen was observed feeding on a planted specimen of the endemic Dietes robinsoniana (C. Moore & F. Muell.) Klatt (Iridaceae) in suburban environment (I. Hutton pers. comm), the early instar specimen utilised leaf fragment smaller than that of similarly-sized larvae of the mainland Australian M. elongatus. The holotype male Metura falcata was collected in December.

Remarks. The single known specimen is worn externally particularly in the forewings, however differences may be observed clearly in the right hindwing termen which is intact aside from scale loss, latter being better represented in the left hindwing. Lord Howe Island is relatively young in geological terms, with no history of connection to any landmass, which suggests a dispersal-based origin for the terrestrial biota of Lord Howe Island. The resulting isolation for new arrivals has resulted in a high level of endemism particularly for invertebrates (DECC 2007; Reid et al. 2018). The similarities in both morphology and in larval bag structure suggest that Metura falcata may share a common ancestor with the mainland Australian M. elongatus rather than the other remote Pacific island species, M. oceanica. Insects larger than ~ 10 mm are at risk from predation by the introduced black rat Rattus rattus (Linnaeus, 1758) on Lord Howe Island (Reid et al. 2018) however insufficient data exists to ascertain if this species is potentially at risk if the rat eradication programme is unsuccessful. Metura falcata is the only species of the family Psychidae known from Lord Howe Island (E.D. Edwards pers. comm).