Dimorphodes elegans, Hennemann, 2021

Hennemann, Frank H., 2021, Stick insects of Sulawesi, Peleng and the Sula Islands, Indonesia- a review including checklists of species and descriptions of new taxa (Insecta: Phasmatodea), Zootaxa 5073 (1), pp. 1-189 : 96-99

Dimorphodes elegans n. sp.

( Fig. 38 )

HT, ♀: Luwu; Sarasin, Luwu, Flach- und Hügelland bis 500 m. Centr. Cel.; Pachymorpha epidicus Gthr. K. Günther det.

[NHMB].

PT, ♂: Posso; Sarasin, II.1895, Posso-See, Centr.-Cel.; Pachymorpha epidicus G. Gthr. K. Günther det. [NHMB].

PT, ♀: S. Celebes, Bua-Kraeng, 5000’ Febr. 1896, H. Fruhstorfer ; Pachymorpha epidicus Gthr. K. Günther det. [ZMPA].

PT, ♀: Sarasin 28.I.–1.II.1895, Luwu, Flachland, Goran-Djaladja, Centr.-Cel.; Pachymorpha epidicus Gthr. K. Günther det.

[SMTD].

Etymology: The name ( elegans lat. = elegant) refers to the comparatively slender habitus of this small new species.

Differential diagnosis: Among the Sulawesian representatives of Dimorphodes this new species is most similar to D. epidicus (Günther, 1935) n. comb. and D. sarasini Redtenbacher, 1908 rev. stat.. From the much smaller epidicus ♀♀ are readily distinguished by the more slender body and limbs, the mesonotum being about 3.2x longer than the pronotum (only 2.8x longer in epidicus ) and almost 3x longer than wide (only 2x longer than wide in epidicus ). In general shape, ♀♀ strongly resemble those of D. sarasini , but they are just slightly more than half the size, have relatively longer and more slender limbs that lack acute teeth (only obtuse lobules), lack any acutely pointed spines on the dorsal surface of the head and thorax and have only one obtuse posteromedian tubercle or swelling on the abdominal terga (two distinct spines on II–V in sarasini ). Males are at first glance separated by the much smaller size, being entire apterous ( Figs. 38C–D ) and lacking the prominent paired spines on the head, pro- and mesonotum and abdominal terga II–V seen in sarasini .

Description: Detailed descriptions of both sexes in German language have already been presented by Günther (1938: 62) along with information on the variability of ♀♀. The following descriptions are mainly based on the specimens in the collection on NHMB.

♀ ( Figs. 38A–C ). Small (body length 49.0–55.0 mm) and slender for the genus with long and slender legs, that lack any distinct armature. Entire dorsal body surface obtusely tectinate longitudinally (less pronounced on abdomen although) and densely but unevenly verruculose and tuberculose. General colour plain mid brown with most of the enlarged tubercles of the head and body ochre (holotype) to dark brown with the dorsal portions of the mesonotum, metanotum and abdominal terga I–V buff (paratype in ZMPA). Antennae greyish mid brown. Armature of body and legs somewhat variable (see comments on variability below) .

Head: Elongate, 1.3 x longer than wide, sub-cylindrical with the genae almost parallel-sided and the vertex rather flattened ( Fig. 38F ); broadest just behind the eyes. Between the eyes with a pair of obtuse, forward directed tubercles; the vertex flattened but slightly raised at posterior, unevenly verruculose to tuberculose and with a pair of enlarged tubercles posteromedially, which together form a V-shaped structure. Genae just weakly granulose. Eyes rather small, slightly oval in outline, weakly projecting and their length contained 2.3x in length of genae. Antennae less than twice the length of head and consisting of 15 antennomeres. Scapus compressed dorsoventrally with the outer lateral margin with an almost semi-circular median deflexion, otherwise roughly rectangular in outline and almost 2x longer than wide. Pedicellus round in cross-section and much shorter. III more slender but almost 1.5x longer than pedicellus, IV very short and only ¼ the length of III. V just slightly longer than IV, VI about 2x the length of IV, the following somewhat longer than VI but roughly uniform in length. Terminal antennomere strongly elongated and longest of all segments, being about as long as preceding four antennomeres combined.

Thorax: Pronotum about as wide but notably shorter than head and slightly widening towards the posterior. The transverse median sulcus distinct, deeply impressed but short, straight and not reaching to lateral margins of segment. Anterior margin with a pair of peg-like tubercles. Dorsal surface otherwise with two closely placed parallel longitudinal rows of obtuse tubercles, that consist of three tubercles in the anterior portion and 2–3 tubercles posterior to the transverse sulcus; the two tubercles just in front of the sulcus the largest. Surface otherwise with a few scattered low tubercles in particular along the lateral margins. Mesothorax elongate, about 3.2x longer than pronotum and weakly widened in the posterior portion. Mesonotum 3x longer than wide, distinctly but obtusely tectinate longitudinally and with a prominent bulge-like swelling anteriorly that is set with a curved transverse row of four strong peg-like tubercles ( Fig. 38F ). Surface densely but unevenly verruculose and in the paratype from Bawakaraeng in the collection of ZMPA with a prominent pair of stout, conical spines post-medially. Close to lateral margins with a longitudinal ridge that is set with tubercles of variable sizes. Mesopleurae irregularly rugulose, sparsely set with a few low tubercles and posteriorly armed with a fairly prominent, conical supra-coxal spine ( Fig. 38C ). Metanotum a little more than half the length of mesonotum, 1.3x longer than wide, tectinate longitudinally, unevenly verruculose and with the same lateral ridge seen on mesonotum. Metapleurae with the supra-coxal spine notably larger than on mesopleurae. Prosternum with a pair of raised oval sensory areas. Meso- and metasternum sparsely and unevenly set with low granules.

Abdomen: Median segment 1.7x wider than long and 1/3 the length of metanotum; posteromedially with an obtuse, spiniform projection. Segment II 1.5x longer than median segment, 1.3x wider than long and rectangular. III–V slightly longer, VI as long as II and VII shortest; III very weakly widening towards posterior and VII notably narrowing, the other roughly rectangular and uniform in width. Sterna minutely and unevenly granulose, Preopercular organ on sternum VII formed by a small scale-like transverse posteromedian swelling ( Fig. 38K ). Tergum VIII 1.3x longer than VII and 1.2x longer than wide, IX roughly quadrate, as wide as VIII; both narrower than all preceding segments. Terga I–IX with a spiniform posteromedian projection, which is largest and most prominent on IX ( Fig. 38B ). VIII–X with an additional ridge-like lateral carina. Anal segment a little shorter than IX, weakly narrowed towards the posterior and the posterior margin with a small and narrow median indention; the lateral margins slightly excavated medially ( Fig. 38J ). Epiproct very small, transverse, scale-like and mostly hidden under anal segment ( Fig. 38J ). Cerci small, compressed laterally and roughly triangular in lateral aspect. Subgenital plate very large and strongly bulgy as typical for the genus with the posterior portion obtusely keeled longitudinally and rounded in lateral aspect; the posterior margin rounded and reaching to tip of abdomen ( Fig. 38K ).

Legs: All long, slender and without prominent armature; profemora almost as long head, pro- and mesothorax combined, mesofemora longer than mesothorax, metafemora reaching to posterior margin of abdominal segment VI and metatibiae projecting considerably beyond apex of abdomen. Profemora strongly compressed and curved basally, only the posterodorsal carina with a few very blunt tooth-like swellings; same carina of protibiae similar but swellings even less pronounced. All four outer carinae of meso- and metafemora spaciously set with blunt toothlike projections, which are smaller on the ventral carinae. Meso- and metatibiae with similar but less pronounced armature but only on dorsal carinae. Basitarsi slender and longer than following three tarsomeres combined.

♂ ( Figs. 38C–D ). Very small (body length 30.0 mm) and slender for the genus, apterous. General colour of the unique known specimen greyish chestnut brown, most of the tubercles of the body ochre. Body much less densely verruculose than in ♀♀ and the dorsal surface less prominently tectinate with only a weak medio-longitudinal keel.

Head: Generally as in ♀♀ with the pair of interocular tubercles more prominent and obtuse but all the remaining armature less pronounced ( Fig. 39G ). Eyes relatively larger, somewhat more projecting and their length contained 2.3x in length of genae. Antennae as long as head and pronotum combined, otherwise as in ♀♀ but with the outer lateral margin of the scapus less deflexed medially.

Thorax: Pronotum as in ♀♀, the longitudinal median line more distinctly impressed however ( Fig. 38G ). Meso-thorax much more slender than in ♀♀ and slightly constricted medially. Mesonotum 5.5x longer than wide, sparsely and unevenly set with variably sized tubercles; two prominent but obtuse, spines at anterior margin ( Fig. 38G ), a pair of blunt tubercles post-medially and a slightly enlarged tubercle at each posterolateral corner. A fine carina close to lateral margins, that is set with several node-like tubercles of different sizes. Metanotum a little more than half the length of mesonotum, 2.3x longer than wide, weakly narrowed medially and with a small pair of median tubercles. Pleurae irregularly granulose and only metapleurae with a very obtuse supra-coxal swelling. Prosternum with the same median pair of sensory-areas that are seen in ♀♀, the meso- and metasternum sparsely set with some irregularly placed granules.

Abdomen: Median segment almost quadrate with anterior margin weakly rounded; each posterolateral corner with a node-like tubercle and posteromedially with a tooth-like swelling. Segment II slightly longer than median segment, III–VI as broad as II uniform in width and length and on average 1.6x longer than wide. VII as long II. Terga II–VII each with a node-like tubercle at each posterolateral angle and with the same tooth-like posteromedian swelling; the latter however gradually decreasing in size towards VI and on VII almost as prominent as on median segment. Sterna II–VII sparsely granulose and each with a pair of obtuse tubercles at posterior margin. Tergum VIII about as long as VII, widening towards the posterior, trapezoidal in dorsal aspect and more distinctly tectiform than preceding terga. IX notably shorter than VIII; both with an additional lateral tubercle at posterior margin. Anal segment tectiform with posterior margin excavated triangularly and the lateral margins in the middle with a hook-like protrusion ( Fig. 38H ) that is set with minute teeth interiorly. Cerci very small, compressed laterally and roughly triangular in lateral aspect. Poculum obtusely conical with the posterior margin strongly keeled longitudinally and the lateral surfaces set with rounded tubercles; the posterior margin with a median indention.

Legs: All long and slender; profemora about as long as head and thorax combined, mesofemora almost as long as pro- and mesothorax combined, metafemora reaching to abdominal segment VIII and metatibiae strongly projecting beyond apex of abdomen. Armature almost as in ♀♀ but dorsal armature less pronounced and ventral carinae with the distant swelling somewhat more distinct. Basitarsi relatively longer and roughly as long as remaining tarsomeres combined .

Variability: Some variability is seen in the colouration, body sculpturing and armature of he limbs in ♀♀. While the holotype is plain mid brown, the paratype from Bawakaraeng in ZMPA has the dorsal surface of the mesonotum, metanotum and basal five abdominal terga buff with the rest of the body is dark brown. Moreover this specimen has all the body sculpturing somewhat more pronounced and has a strong pair of post-medial spines on the mesonotum. Moreover, also the armature of the limbs is comparatively more distinct. The paratype in SMTD even has an additional pair of spines on the metanotum .

Comments: All the specimens subsequently assigned to his D. epidicus by Günther (1938: 61) are a distinct and previously unnamed species, that is herewith described. Eggs unknown.

Distribution: Central Sulawesi, Prov. Sulawesi Tengah, Luwu 500 m [NHMB]; Central Sulawesi, Prov. Su-lawesi Tengah, Lake Poso [NHMB]; S-Sulawesi, Prov. Sulawesi Selatan, Gunung Bawakaraeng “Bua Kraeng” [ZMPA]; Central Sulawesi, Prov. Sulawesi Selatan, Luwu, Djaladja, lowland [SMTD].

Figures

FIGURE 38. Dimorphodes elegans n. sp. [NHMB]: A. ♀ (HT), dorso-lateral view; B. ♀ (HT), lateral view; C. ♀ (HT), dorsal view; D. ♂ (PT), lateral view; E. ♂ (PT), dorsal view; F. Head, prothorax and anterior portion of mesothorax of ♀ (HT) seen laterally; G. Head, prothorax and anterior portion of mesothorax of ♂ (PT) seen laterally; H. Terminal abdominal segments of ♂ (PT) in lateral view; J. Terminal abdominal segments of ♀ (HT) in dorsal view; K. Terminal abdominal segments of ♀ (HT) in ventral view.

FIGURE 39. Dimorphodes sarasini Redtenbacher, 1908 rev. stat.: A. Egg, dorsal view [coll. FH, No. 1318-E]; B. Egg, lateral view [coll. FH, No. 1318-E]; C. ♂ (LT of synonym D. bellicosus Redtenbacher, 1908), dorsal view [NHMW, No. 728]; D. ♂ (LT of synonym D. bellicosus Redtenbacher, 1908), lateral view [NHMW, No. 728]; E. ♀ from Luwu, dorsal view [MNHU]; F. Terminal abdominal segments of ♀ (HT) in lateral view [NHMW, No. 732]; G. Terminal abdominal segments of ♂ (LT of synonym D. bellicosus Redtenbacher, 1908) in lateral view [NHMW, No. 728]. (Figs. C–D, F–G © Paul D. Brock).