Gnathothlibus samoaensis, Lachlan, 2009

Lachlan, Robert B., 2009, Two New Species of Gnathothlibus Wallengren from Fiji and Samoa and a New Species of Theretra Hübner from New Guinea (Lepidoptera: Sphingidae), Records of the Australian Museum 61 (1), pp. 73-87 : 75-80

Gnathothlibus samoaensis n.sp.

Figs 5–9 , 16

Type material. HOLOTYPE?, SAMOA: Approx. 10 km S-W of Apia , Upolu Is. Alt. 410 m. 13°52'53.9"S 171°49'26"W 18 Nov. 2008, R. B. Lachlan, AM K266028 . PARATYPES 52 ??, 4 !!, all with same data as holotype but dated between 13th and 19th November, 2008. 4 ?? and 1! ( AM K266029 – K266032 , and K266033!) in AM , remainder in RBLC.

Other material examined. 3 ??, WESTERN SAMOA: Mulivai Beach area, central south coast of Upolu Island, 9, 12 May, 1985, R.B. Lachlan, in RBLC.

Diagnosis. Head, thorax and abdomen uniform olive-green. Forewing upperside olive green in colour with prominent darker markings. The unicolorous band enclosing the stigma is about 5 mm wide along vein CuA 1. Hindwing upperside ground colour orange; a dark, slightly variable, well-developed terminal band from apex to tornus at least 2 mm wide with most specimens exhibiting some dark scaling along inner margin from tornus. Female forewing upperside with ground colour and pattern in shades of darkish brown, lacking olive green tinge of male but with a lustrous appearance in fresh specimens, particularly on the median and marginal areas of wing.

Description. Male. (Figs 5,6,9,16). Antennae creamy-brown above, brown below; palpi olive green above, contrasting off white below; dorsal surface of head and prothorax darker olive green, remainder of thorax and abdomen uniform olive green; small dark median spot with vestigial posterolateral orange-brown on prothorax; thin lateral creamy-olive stripe from base of antenna to costa of forewing, continuing as creamy-white on the outer edges of the tegula above both wings. Thorax ventrally with creamy, light brown patch immediately posterior to palpi, remainder of narrow median band creamy-olive edged laterally with reddish-brown pilosity, dissipating as it reaches upper abdominal segments. Abdominal segments laterally ( Fig. 9 ) each with distinct orange-brown posterior margin contrasting with olive green ground colour; abdomen with three small lateral black spots surrounded clearly by white. Fore-tibae covered in long, creamy, light olive hairs cales with very distinct dark, distal, ventral edge; proximal three segments of fore-tarsi covered in short, creamy hair scales above, edged ventrally with cream hair scales suffused with dark scales, shortest on distal segment, longest on proximal segment.

Forewing upperside as in Fig. 5 . Forewing length 35.4–44.3 mm, mean 40.4 mm (n = 68). Ground colour olive green (brighter in fresh specimens) with darker markings on distal area of wing; some specimens appear browner but dark olive-green scaling is still clearly present on the forewings and body to varying degrees; small black stigma with light coloured centre at end of discal cell; small, dark, postmedian line from costa to vein M 1 becoming a line of dark dots on each vein to vein 1A+2A; irregular submarginal patch of dark scales from vein M 1 to vein CuA 1; this patch is variable; a prominent, dark, straightish oblique median line runs from costa, where it is curved distally, to inner margin; a short, irregular, subbasal band edged on each side by thin dark lines and curved gently distally, runs from costa to the dark basal patch below vein 1A+2A. The unicolorous band enclosing the stigma is about 5 mm wide along vein CuA 1. Forewing underside as in Fig. 6 ; ground colour burnt orange basad, distally overlaid heavily with darker olive-brown scales with usually two distinct dark, irregular, parallel post median lines from costa to veins CuA 1 or CuA 2 and a single distinct, dark, irregular, submarginal line from apex to tornus; all three lines are usually well developed, particularly the submarginal line but may be reduced in some specimens.

Hindwing upperside as in Fig. 5 ; ground colour orange; a dark, slightly variable, well-developed terminal band from apex to tornus at least 2 mm wide, slightly thinner near apex with most specimens exhibiting some dark scaling along inner margin from tornus; inner edge of terminal band clearly spikes basally along vein 1A+2A. Hindwing underside as in Fig. 6 ; ground colour orange-brown, very heavily speckled with dark brown and olive scales; marginal area darker from apex to tornus; dark, mostly straight, median line, thickest at costa, curving distad from costa to vein RS and usually reaching vein CuA 2 but does not touch distal edge of cell; a much less prominent, small, parallel, dark post median line to vein M 1, well developed in many specimens, vestigial in some specimens.

Male genitalia as in Fig. 16 . Uncus, in lateral view, long, slender, parallel sided for the basal half of its length, slightly but clearly arched, distal end swollen, distal margin clearly convex with rounded, slightly pointed dorsal crest; small, sharply pointed ventral tooth at distal margin; gnathos, in lateral view, thin, almost straight, dorsal surface tapering to a small, slightly upturned point at distal margin, ventral surface slightly concave; valva dorsal margin straight proximally then clearly upwardly convex, distal margin rounded, ventral margin slightly convex; sacculus well developed; harpe robust, distal end smooth surfaced and spine-like, upturned; aedeagus in lateral view, with distal end tapered to a bluntly rounded apex with backward directed dorsal fishhook-like barb, ventrally with a small, similar barb, a little proximad of dorsal barb.

Female. (Figs 7,8). Forewing length 43.6– 46 mm, mean 44.7 mm (n = 4). Head, thorax and tegulae dark brown. Abdomen above dark grey-brown. Thin lateral creamyyellow stripe from base of antenna to posterior edge of tegulae above hindwings. Thorax below reddish-brown suffused ventrally with mauve hair scales; abdomen ventrally mauve-brown, each segment with orange-brown hair scales on posterior margin with four well-developed lateral white spots with small black centres. Fore-tibiae covered in short cream hair scales with some dark scales on distal posterior edge; fore-tarsi without hair scales.

Forewing upperside as in Fig. 7 ; ground colour and pattern in shades of darkish brown, lacking olive green tinge of male but with a lustrous appearance in fresh specimens, particularly on the median and marginal areas of wing; small dark brown stigma with light centre at end of discal cell; a distinct lighter, lustrous brown band, enclosing the stigma, runs from costa to inner margin, marginal band from apex to tornus, with inner irregular line, of same colour. Forewing underside as in Fig. 8 ; ground colour reddish-brown, marginal band from apex to tornus mauve-brown and often overlaid distinctly with olive scales, a dark brown, irregular, submarginal line runs from apex to tornus; two variable dark brown parallel post median lines run from costa, often reaching vein CuA 2.

Hindwing upperside as in male but dark brown terminal band much broader, with inner margin slightly irregular and suffused with orange scales, this dark band spikes distinctly basad along vein 1A+2A. Hindwing underside as in Fig. 8 ; ground colour slightly more mauve than forewing and heavily speckled along costa with dark scales; slightly variable yellowish streak, mostly along proximal side of vein 1A+2A.

Etymology. The specific name samoaensis is derived from the Pacific Island nation of Samoa, formally Western Samoa, the only recorded locality for the species.

Distribution. At present G. samoaensis is only recorded from the island of Upolu, Samoa, but being a common species it would certainly be found on the nearby larger island of Savai’i, just 22 km west of Upolu.

Figures

Fig. 5. Gnathothlibus samoaensis n.sp. holotype male, upperside.

Fig. 6. Gnathothlibus samoaensis n.sp. holotype male, underside.

Fig. 7. Gnathothlibus samoaensis n.sp. paratype female, upperside.

Fig. 8. Gnathothlibus samoaensis n.sp. paratype female, underside.

Fig. 9. Gnathothlibus samoaensis n.sp. holotype male, lateral view showing colouration of abdominal segments.

Fig. 16. Gnathothlibus samoaensis n.sp.