Leprocaulinus digitatus, 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 : 34-35

Leprocaulinus digitatus n. sp.

( Fig. 14 )

Carausius heinrichi, Günther, 1938: 81 (in part).

Carausius immundus, Günther, 1938: 58 , 81 (in part).

HT, ♀: Sarasin—Luwu, Central-Celebes; Carausius immundus Br. K. Günther det.; Carausius sp. cf. K. Günther, Mitt. Zool. Mus. Berlin XX, 1935, p. 8. K. Günther det. [NHMB].

PT, ♀: Luwu +; Sarasin—Luwu, Central-Celebes; Carausius immundus Br. K. Günther det.; Carausius sp. cf. K. Günther, Mitt. Zool. Mus. Berlin XX, 1935, p. 8. K. Günther det. [NHMB].

PT, ♀ (penultimate instar): Sarasin 28.I.–1. II .1895, Luwu, Flachland, Boran Djaladja, Centr. Cel.; Carausius heinrichi K. Gthr. K. Günther det. [NHMB].

Etymology: The name ( digitatus lat. = with fingers) refers to the long and apically bifid, digitiform projecting preopercular organ of ♀♀ of this new species.

Differential diagnosis: Females (the only sex known) of this new species are very similar to those of L. sulawesiense n. sp. but differ by the very prominent Preopercular organ on abdominal sternum VII, which is formed by a long, digitiform and apically bifid projection ( Figs. 14D, F ), as well as the somewhat more prominent cephalad pair of spines.

Description: ♀ ( Figs. 14A–C ). Medium-sized for the genus (body length 132.5–149.0 mm), form fairly slen-der with a short median segment and only a pair of low swellings between the eyes. Body surface unevenly tuberculose and granulose, sculpturing variable and occasionally with scale-like swellings and excrescences of variable sizes on abdominal terga I–VII. Colour ranging from buff to greyish brown; occasionally flecked with ochre and in the adult paratype with some irregularly scattered white dots on the thorax and four basal abdominal segments ( Fig. 14C ). Large tubercles of the head and thorax pale ochre or black. Antennae dull ochre with a few faint dark brown annulae. Eyes dark brown.

Head: About 1.25x longer than wide, subcylindrical with the genae indistinctly narrowing towards posterior. Frons with two small but deep transverse impressions between bases of antennae. Between the eyes with a slightly swollen transverse area that bears two fairly low and obtusely conical swellings; posteriorly this raised area is bordered by a V-shaped furrow, that expands almost from one eye to the other. Vertex flat and with a prominently impressed coronal line, otherwise set with a few scattered nodes and small tubercles, genae usually with 2–3 obtuse nodes. Posterior margin with a notably enlarged pair of obtuse median swellings. Eyes roughly circular in outline, moderately projecting and their diametre contained almost 2.5x in length of genae. Antennae reaching to anterior margin of median segment. Scapus compressed dorsoventrally, somewhat deflexed laterally oval in outline and 1.7x longer than wide. Pedicellus oval in cross-section and a little more than 1/3 the length of scapus.

Thorax: Pronotum of similar dimensions as head, with the anterior portion somewhat expanded, the lateral margins notably concave and about 1.4x longer than width of anterior margin. Transverse median sulcus distinct, weakly curved and almost expanding over entire width of segment; anterior margin with a median pair of blunt tubercles and some further paired tubercles on dorsal surface. Mesothorax elongate, slender and about 5.3x longer than prothorax. Mesonotum with a fine but distinct longitudinal median carina and unevenly set with tubercles and nodes of variable sizes. Mesopleurae with a longitudinal median row of rather small nodes; mesosternum acutely keeled medio-longitudinally but otherwise smooth except for a few indistinct granules in posterior portion ( Fig. 14G ). Metanotum half the length of mesonotum and about 4x longer than wide; sculpturing less pronounced than on mesonotum. Metapleurae and sternum sparsely nodulose.

Abdomen: Median segment about 2x longer than wide, somewhat less than half the length of metanotum and gently constricted medially; sculpturing alike and occasionally with a transverse scale-like crest or swelling at posterior margin. Abdomen excluding median segment equal in length to head and complete thorax combined; entire dorsal surface with a fine and acute longitudinal median carina and irregularly granulose to tuberculose. Occasionally each with a posteromedian swelling or scale-like excrescence which is most prominent on tergum VI. Segment II 1.6x longer than median segment, II–VI uniform in width, II–III and IV–V equal in length, on average some 2.7x longer than wide. Tergum VI usually somewhat swollen post-medially and VII shorter and slightly narrower than all previous. Sterna sparsely and irregularly tuberculose and slightly rugulose. Preopercular organ formed by a long, digitiform and apically bifid projection, which is posterior directed and placed in a small distance before the posterior margin of sternum VII ( Figs. 14D, F ). Tergum VIII half as long as VII and slightly widening towards the posterior, IX shorter and slightly transverse in dorsal aspect. Anal segment about as long as IX, strongly convex longitudinally and somewhat narrowed posteriorly, with the posterior margin widely triangularly excavated and the outer angles obtusely angular ( Fig. 14E ); the lateral margins slightly deflexed in the basal portion ( Fig. 14F ). Epiproct distinct, somewhat variable in length and shape, usually wider than long and projecting notably behind apex of anal segment; roughly triangular in outline ( Fig. 14E ). Cerci small, compressed laterally and conical with the apex acute. Subgenital plate strongly keeled medio-longitudinally, convex, bulgy and more or less angular in the median portion ( Fig. 14F ); the posterior margin narrowed and projecting slightly beyond apex of abdomen ( Figs. 14D–F ).

Legs: All moderately long and slender, the profemora about as long as mesothorax, metafemora reaching about half way along abdominal segment IV and metatibiae reaching to abdominal segment VII. Anterodorsal carina of profemora moderately deflexed and more or less undulate and wavy in the basal one third; the posteroventral carina with two obtuse sub-apical teeth. The dorsal carina of the protibiae strongly but almost uniformly deflexed and lamellate. Meso- and metafemora slender, laterally compressed and unarmed except for two obtuse sub-apical teeth on the two outer ventral carinae ( Fig. 14G ). Medioventral carina moderately developed. Probasitarsus about equal in length to combined length of following three tarsomeres and with the dorsal carina strongly raised, rounded and semi-circular in outline ( Fig. 14G ). Meso- and metabasitarsus slender and about as long as following three tarsomeres combined.

Variability: The two adult ♀♀ at hand show quite some variability in size (table 4), the paratype being notably longer than the holotype. Both specimens have been preserved in spirits why only limited observations can be made on the colouration. The holotype is greyish mid brown ( Figs. 14A–B ) while the paratype is lighter in colour and rather buff ( Fig. 14C ). The latter specimen is also remarkable for having some scattered white dots on the thorax and four basal abdominal terga ( Fig. 14C ). The body sculpturing is generally more pronounced in the holotype. The paratypic penultimate instar nymph (body length 98.0 mm) is remarkable for showing a distinctive body sculpturing that is not seen in the two adult examples. The meso- and metanotum bear a few irregularly placed black conical tubercles and there is a scale-like transverse posteromedian excrescence on abdominal terga I–VII, which is small on II–V and VII (smallest on IV and V) but distinct on the median segment (= tergum I) and VI. The excrescence on tergum VI is the largest and towards the anterior has a further almost semi-circular medio-longitudinal keel, giving it a T-shaped outline in dorsal aspect. The typical digitiform Preopercular organ seen in the adult specimens is still undeveloped in this immature example and the colouration is a yellowish mid brown and particularly with the limbs irregularly flecked with ochre.

Comments: Males and eggs unknown.

Distribution: Central Sulawesi, Prov. Sulawesi Selatan, Luwu Regency [NHMB].

Figures

FIGURE 14. Leprocaulinus digitatus n. sp.: A. ♀ (HT), dorsal view [NHMB]; B. ♀ (HT), lateral view [NHMB]; C. ♀ (PT), dorso-lateral view [NHMB]; D. Terminal abdominal segments of ♀ (PT) in lateral view [NHMB]; E. Terminal abdominal segments of ♀ (PT) in dorsal view [NHMB]; F. Terminal abdominal segments of ♀ (HT) in lateral view [NHMB]; G. Ventral view of head, pro- and mesothorax of ♀ (PT) [NHMB].