Eurycantha portentosa Kirby, 1904

Brock, Paul D. & Dewhurst, Charles F., 2024, A first description of the male of the Rossel Island Stick-insect, Eurycantha portentosa Kirby, 1904 (Phasmida: Lonchodidae)., Zootaxa 5543 (2), pp. 296-300 : 296-299

Eurycantha portentosa Kirby, 1904

is reported on in this work, as the largest and broadest Eurycantha species known so far, with two 170 mm. female syntypes (lat. mesonotum 22–26 mm.) briefly described from Rossel Island on pp. 442–443 and with no further material yet been reported in the literature. The volcanic Rossel Island (32 km. long by 14 km.), otherwise known as Yela , is the easternmost island in the Louisiade Archipelago , 370 km. off the South-eastern tip of Papua New Guinea, and a part of Milne Bay Province. Due to its geographic isolation, the island is known to harbour many endemic animals and plants (e.g. Johns et al., 2009) and much is still tropical rainforest, with mountainous areas up to 800 m. The data labels show the original specimens were collected in 1889 and presented to the Natural History Museum, London by Basil Thompson ( Brock et al. 2016). Sir Basil Thompson was a British colonial administrator and prison governor, who assisted Sir William Macgregor, who was appointed administrator of British New Guinea in 1888. Kirby’s description is as follows ‘Black; antennae, legs, and under surface inclining to ferruginous; spines arranged nearly as in the last species [ Eurycantha willeyi Kirby, 1904 from New Britain, a synonym of E. calcarata ]; much more strongly granulated on the upper surface, and with a transverse row of short spines before the extremity of most of the abdominal segments. There are sometimes additional small spines between the three larger ones on the sides of each abdominal segment.’

In view of the brief description given, it is appropriate to re-describe the female, designate a lectotype and formally describe the male.

Lectotype. ♀ [ Papua New Guinea], LouisiadeArchipelago , Rossel Island, BMNH (E) #844597 ( NHMUK 012500251), [18]89-89, (Pres. Basil Thompson, Esq.), here designated, in order to preserve stability of nomenclature (this specimen re-measured and found to be 175 mm with maximum lateral width of mesonotum 26 mm.)

Paralectotype. ♀ [ Papua New Guinea], Louisiade Archipelago , Rossel Island, BMNH (E) #844598 ( NHMUK 012500250), [18]89-89, (Pres. Basil Thompson, Esq.) (this specimen with maximum lateral width of mesonotum 22 mm.)

Non-type material examined. ♂ ♀ Papua New Guinea, Louisiade Archipelago , Rossel Island, Abaleti, 11.395 S, 154.200 E, 30.iv.2023, D.K. Mitchell ( NHMUK) , ♂ ♀ same data (ex. collection C.F.Dewhurst) ( OUMNH) .

Female description. Large and broad, typical robust-looking, spiky, wingless Eurycantha species, black or mid-brown colouration, with a beak-like ovipositor. Large spines present on the whole body particularly laterally, also legs, which have thickened femora; stout tubercles also present. ( Fig 1 ).

♀ ( Fig. 1 ). Head large, longer than wide, with several spines, a pair between the eyes and about six towards the back; tubercles also present. Eyes large, brown. Antennae almost as long as forelegs [some segments broken off and missing] with 28+ similar-length segments, of which the basal segment is broader than 2 nd segment. Pronotum slightly longer than head and much broader, expanding gradually towards hind part. Lateral corners with short spine, then three larger lateral spines each side, the hind ones larger. Segment rugged, with swollen raised areas, ridges and scattered tubercles, the latter more extensive on remainder of thorax and abdomen; ventral surface is fairly smooth and glossy, hind part of mesothorax with large brown ‘X’ mark, metathorax ‘M’-marked. Mesonotum broader than and almost twice the length of pronotum with 8-9 large lateral spines each side; Metanotum and median segment combined slightly longer than half length of mesonotum and slightly broader. Metanotum with three paired spines each side laterally, the inner spine much shorter; further large spines also present beneath on metapleurae. Abdomen broad with 3 large lateral spines on each segment, sometimes with smaller spines in between or alongside. Segments tapering from 6 th, anal segment only half width of 6 th. Anal segment slightly longer than 9 th and rounded at tip, leading to a rigid, projecting beak-like ovipositor, tapered at its tip; operculum not quite reaching the tip ( Figs. 1C–E ). Ovipositor almost the combined length of abdominal segments 8–10. End of each abdominal segment typically with 5 well-spaced spines across, the largest furthest from the central spine. Cerci small, leaf-like. Legs robust, of modest length and spiny. All femora broadened, particularly hind femora. Spines typical for Eurycantha , hindlegs with more spines, upper part of hind femora with 5 or more spines, beneath with 3 large spines, the furthest largest. Hind tibiae with 7 well-spaced spines before subapical pair.

NOTE. A small 132 mm., mid-brown ♀ with the same data appears to belong to the same species, but the spines are smaller and fewer in some cases, for example, the mesonotum has only 6 spines on the left hand margin and 7 on the right. This specimen has also been deposited in the Natural History Museum, London (NHMUK).

Male description. Large and broad, typical robust-looking, spiky, wingless Eurycantha species, black (likely to be mid-brown in some specimens) colouration. Large spines present on the whole body particularly laterally, also on the legs, which have massively thickened femora, particularly the hind pair. Each femur with a very large spur beyond a small subapical spine; stout and small tubercles are also present. ( Fig. 2–3 ).

♂ ( Fig. 2–3 ). Similar-sized or only slightly smaller than the female, with only abdomen width noticeably smaller. Head large, slightly longer than wide, with several spines, a pair between the eyes and four towards the back; tubercles also present. Eyes large, brown. Antennae probably almost as long as forelegs [most segments are broken off and missing]; basal segment is broader than 2 nd segment. Pronotum noticeably longer than head and 1.5 x broader. Lateral corners with short spine, then three larger lateral spines each side, the hind ones larger. Segment rugged, with swollen raised areas, ridges and scattered tubercles, as in female the latter more extensive on remainder of thorax and abdomen; ventral surface is fairly smooth and glossy, hind part of mesothorax with large brown ‘X’ mark, metathorax also ‘X’-marked with two raised, rounded, swollen areas above the mark. Mesonotum broader than and 2 x the length of pronotum with 7 very large, slightly curved lateral spines on each side ( Fig. 3B ). Metanotum and median segment combined slightly longer than half length of mesonotum and slightly broader. Upper part of metanotum with three paired spines each side laterally, the inner spine much shorter; further large spines also present beneath on metapleurae. Abdomen broad, but only up to 15 mm. wide (compared to metanotum 21 mm.) with 3 large lateral spines on each segment, sometimes with smaller spines or swollen areas in between ( Fig. 3C ). Segments slightly wider towards 6 th, then tapering; anal segment not quite 0.75 width of 6 th. Anal segment much longer than 9 th; gently emarginate at tip, in middle a supraanal plate is visible beneath, laterally curved and thickened; poculum rounded at tip, reaching just over half length of anal segment ( Figs. 3D–F ). End of each abdominal segment typically with 5 well-spaced spines across. Cerci small, leaf-like, rounded at tip. Legs robust, of modest length and spiny. All femora are broadened, particularly much longer, massively swollen hind femora ( Fig. 3G ). Hindlegs spinier, upper part of hind femora with 5 or more serrations, beneath with 5 well-spaced spines, the largest spur about as long as width of femora. Hind tibiae with 7 well-spaced spines before subapical pair, two noticeably larger.

Measurements (mm): ♀: Body length 155–175 (including ovipositor), head 13–14, antennae? [broken off], pronotum 16–18, mesonotum 30–32, metanotum and median segment about equal, combined 15–17. femora: fore 26–28, mid 24–26, hind 34–36, tibiae: fore 26–28, mid 23–25, hind 34–40, tarsi: fore 15–16, mid 15–17, hind 15–18, cerci 2. ♂: Body length 142–143, head 12, antennae? [broken off], pronotum 15, mesonotum 31, metanotum and median segment about equal, combined 17. femora: fore 27, mid 24, hind 41, tibiae: fore 29, mid 26, hind 42, tarsi: fore 15, mid 16, hind 18, cerci 2.

Comments on the name. Named from the Latin portentôsus, meaning ‘extraordinary, monstrous, unnatural’. The Yele language, or Yélî Dyne, is the language spoken on Rossel Island, where the phasmid is known as ‘puee’.

Habitat. Associated with wild palms, which are abundant.

Eurycantha as food and use by man. Lucy Mitchell (pers. comm., 2024) used to live on rain-forested mountains in SE Papua New Guinea with her grandmother. After rain she would be sent out to look for snails, small frogs and Eurycantha . The phasmids were placed on the fire and turned until cooked. Once cracked open, (including from the legs), the meat would be pulled out, ready to eat; most likely this practice would be replicated in other parts of Papua New Guinea, Indonesia and some islands. Natives in the hill-villages of northern Goodenough Island used the spurred hind femora of Eurycantha latro Redtenbacher, 1908 for line-fishing in freshwater streams ( Balfour, 1915). However, examination of images in that paper shows this species is almost certainly misidentified. E. latro was described from Andai, West Papua, Indonesia. Goodenough Island is in the Solomon Sea, the westernmost of three large islands of the D’Entrecasteaux Islands in Milne Bay Province, Papua New Guinea. The figured species shows large spines similar to those of Eurycantha horrida Boisduval, 1846 which may represent a species complex across Papua New Guinea, Indonesia and nearby islands.

Discussion. Redtenbacher (1908) provided a useful key to Eurycantha species, with groups initially split mainly into either having the pronotum margin 3-spined ( E. horrida , E. latro and E. calcarata ) or 4–6 spined in other species. E. portentosa (omitted by Redtenbacher) clearly groups with other 3-spined species, which are all larger species, with broadened femora, compared with smaller, less robust-looking species in the largest group. The genus is in need of revision and it is probable there are several more species than are known at present. Whilst E. portentosa was thought to stand out from other species because of its larger size, it is evident from the series now seen that this species varies in size, possibly due to the quality of foodplant, which is also the case in E. horrida . Larger specimens of E. horrida in PDB’s collection reach up to an impressive 158 mm. in females, 123 mm. in males. Redtenbacher gave 130–135 mm. and 100–110 mm. respectively. Before seeing males of E. portentosa , the authors envisaged them having massive spurs on the hind femora, as characteristic in E. horrida (the spurs are much longer than width of femora). However, although spurs are large, this is not quite the case, but the characteristic large lateral spines on the mesonotum in E. portentosa are larger than in E. horrida and other known Eurycantha species. In E. horrida , large lateral spines on the mesonotum are a similar size in both sexes, whereas in E. portentosa these are proportionately much larger in males. Eggs are useful in taxonomy and usually show differences between related species, but unfortunately, they are not yet available for E. portentosa .

Figures

FIGURE 1: Female Eurycantha portentosa: A. dorsal view (lectotype #844597, copyright NHMUK), B. female, lateral view, C–E. end of abdomen: C. dorsal, D. lateral, E. ventral view.

FIGURE 2: Male Eurycantha portentosa: dorsal view, photo by JT.

FIGURE 3: Male Eurycantha portentosa: A. lateral view, photo by JT, B. large thorax spines, C. abdominal segment 1–3 spines, with typical lateral spines on segments 2–3, D–F. end of abdomen: D. dorsal, E. lateral, F. ventral view, G. hind femur with conspicuous spur.