Xeroderus Gray, 1835

Brock, Paul D. & Hennemann, Frank H., 2023, A new species of Xeroderus Gray, 1835 (Phasmida: Phasmatidae: Xeroderinae) from Papua New Guinea and notes on the genus, Zootaxa 5258 (4), pp. 443-454 : 444-445

Xeroderus Gray

( Figs. 1–6 )

Type species: Xeroderus kirbii Gray, 1835 [= Xeroderus kirbyi Gray ], by original monotypy.

Xeroderus Gray, 1835: 32 ; Otte and Brock, 2005: 341; Brock and Hasenpusch, 2009a: 180; Brock & Büscher, 2022: 561. (Additional checklist and other references in Brock et al., 2023)

Cooktownia Sjöstedt, 1918: 43 . (Synonymised by Brock & Hasenpusch, 2007: 75)

Generic characteristics. Based on morphology, closely related to the genus Nisyrus Stål, 1877 , which also has lateral lobes on abdominal segments, originally erroneously thought to be gill-like appendages indicating a semi-aquatic lifestyle ( Waterhouse, 1895). Females of Nisyrus are easily distinguished by its broader body and the presence of only rudimentary alae, that reach no further than the 3 rd abdominal segment and males of Nisyrus lack the large, leaf-like cerci seen in Xeroderus . The eggs of Xeroderus readily differ from the almost spherical eggs of Nisyrus by being sub-cylindrical and elongate in shape. Moreover, Xeroderus only occurs in eastern Australia and Papua New Guinea while Nisyrus is distributed throughout the Pacific Ocean with records from Fiji, Tonga, Vanuatu and the Solomon Islands.

Description (♂, ♀). Medium sized, large-winged Xeroderinae (body length ♁ 52.0–70.0 mm, ♀ 85.0–106.0 mm), some specimens with distinct dark and pale mottling pattern on body and tegmina as well as costal region of alae, resembling lichen. Head rounded, about as long as wide, with sparse tubercles on vertex, eyes large; three distinct ocelli present, the hind pair larger. Antennae longer than length of profemora in ♀, in ♁ longer and bristly, reaching beyond length of outstretched protibiae; segments variable in length (24–28 segments), with broad basal segment and variable length subsequent segments. Pronotum slightly shorter than head or about same length, with central impression; sparse tubercles and a pair of central spines in one species ( X. conlei sp. n.). Mesonotum broader than head and pronotum (less so in ♁), less than 2x length of pronotum, with raised central area, armed with short to larger, broad lateral spines and several on the disc i.e. main part of raised area; outer and lateral spines/tubercles more numerous and conspicuous and varying in thickness. Lateral margins of meso- and metathorax with series of lobes. Ventral surface of head, thorax and abdomen smooth, lacking tubercles, flattened. Metathorax similar length to mesothorax with lateral lobes or spines. Median segment similar length to metathorax. Tegmina broad, oval; alae large reaching up to end of 9 th abdominal segment; brownish or transparent, occasionally with coloured inner margin. Abdomen elongate, parallel-sided. Both sexes with large fin-like lateral lobes on abdominal terga, although the lobes can be more rounded, but much smaller on segments 9–10 or just 10. Male anal segment shorter than 9 th segment, distinctly tectiform medio-longitudinally and narrow, split into large hemi-terga forming an arch-like structure; these denticulated interiorly. No vomer in ♁. Poculum swollen, subtruncate at broad tip, not reaching end of 9 th abdominal segment. Female subgenital plate with rounded or tapered tip, reaching end of abdominal segment 9 or end of abdomen. Cerci of ♁ leaf-like, shorter than or just exceeding length of anal segment. Legs moderately long and slender, with hindlegs just about reaching end of abdomen in ♁, end of segment 7–8 in ♀. Femora with well spread paired spines, some similarly shaped to abdominal lobes. Tarsi well over half length of tibiae (fore tarsi longest), slender, not lobed.

Egg ( Figs. 1 E-G). Fairly large (length> 8.0 mm) and elongate. Capsule sub-cylindrical,>2x longer than wide or high, gently arched longitudinally, with raised sculpturing and some pitting; polar area with a distinct transverse indention. Micropylar plate small and oval, only about one-sixth the length of capsule and somewhat displaced towards the polar end of capsule. Operculum roughly circular with some obtuse swellings and a small, narrow peglike capitulum in centre.

Comments. The much broader Xeroderus brevipennis Redtenbacher, 1908: 359 (type locality: Santa Isabel Island, Solomon Islands) is found to be a member of Nisyrus Stål, 1877: 66 and is here transferred from Xeroderus . N. brevipennis (Redtenbacher) comb. n. is the first record of Nisyrus Stål from the Solomon Islands. Following synonymy proposed in Brock & Büscher, 2022, the additional five Nisyrus species from Fiji, Tonga and Vanuatu ( Brock et al., 2023) require revision.

Figures

FIGURE 1: Xeroderus kirbyi Gray, 1835. A. ♀ Queensland, 14 km S. of Bundaberg, 1.ii.1971, H. Frauca, on trunk of Eucalyptus citriodora dorsal view [ANIC], photo by PDB; B. Head & thorax of ♀ Queensland, Garradunga, J. Hasenpusch, dorsal view [O. Conle collection] photo by Oskar Conle; C. End of abdomen of lectotype ♀, lateral view [OUMNH], photo by PDB, Phasmida Species File; D. End of abdomen of same specimen, ventral view [OUMNH], photo by PDB; E. F. Eggs from Queensland, Garradunga, photo by Jack Hasenpusch; G. Eggs from Queensland, Herberton, photo by Ethan Beaver. Captions for figures (PDB = Paul D. Brock, FHH = Frank H. Hennemann)

FIGURE 2: Xeroderus kirbyi Gray, 1835. A. ♁ Queensland, Garradunga, in dorsal view [F. Hennemann coll. No. 0839-2]; B. C. D. End of abdomen of same ♁ lateral, dorsal and ventral views; E. F. G. Head & thorax of same ♁ lateral, dorsal and ventral views. All photos by FHH.

FIGURE 3: Xeroderus conlei sp. n. A. ♀ holotype, dorsal view [MNHU]; B. ventral view; C. lateral view; D. Head & thorax, in dorsal view; E. F. G. End of abdomen lateral, dorsal and ventral views. All photos by Oskar Conle.

FIGURE 4: Distribution map of Xeroderus species.

FIGURE 5: Queensland, Golden Hole, Biggs Recreation area, Bartle Frere. Riverine lowland tropical rainforest habitat of Xeroderus kirbyi, photos by Ross Coupland.

FIGURE 6: A. B. Live specimens of Xeroderus kirbyi in nature, showing superbly camouflaged female and male, photos by Ross Coupland; C. on boulder, photo by Sophie Kalkowski-Pope.