Mnesilochus luwuense, 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 : 44-46

Mnesilochus luwuense n. sp.

( Fig. 18 )

Lonchodes haematomus, Günther, 1938: 78 .

HT, ♀: Sarasin, Luwu , Central-Celebes ; Lonchodes hosei Kby. K. Günther det. [ NHMB, No. VI.D.133] .

Etymology: Named after the Luwu Regency, the type-locality and only known record of this new species.

Differential diagnosis: Similar in general shape and appearance to the Philippine M. haedulus Stål, 1877 (as described and illustrated by Hennemann & Conle, 2007: 73, figs. 107–113) and the Palawanese M. palawanicus (Carl, 1913) but readily separated from these and from all other known members of the genus by the morphology of the mesofemora. While these species have the dorsomedian lobe roughly triangular in shape with the posterior margin dentate, this lobe is distinctively bifid with a median excavation in M. luwuense n. sp. ( Fig. 18D ).

Description: ♀ ( Fig. 18 ). The unique holotype has provisionally been preserved in spirits, what might have caused discolouration. Moreover, ♀♀ of this genus are known to show considerable morphological and chromatic variability, why the description here presented on basis of the holotype can in several aspects only be exemplary for this species.

Of medium size (body length 102.0 mm) and moderately stocky shape for the genus with a large, bifid dorsal lobe of the mesofemora. Entire body surface unevenly granulose, tuberculose, verruculose and rugulose; abdominal terga II and V–VIII with posteromedian protrusions. General colour of the holotype greyish mid brown with the posterolateral portions of the mesothorax, lateral portions of abdominal sterna II–IV buffy. Mesonotum with four small blackish dorsal markings in anterior half and a narrow black lateral marking some distance before the posterior margin. Metanotum with two black spots sub-anteriorly and a black spot at each posterolateral angle. Median portion of abdominal tergum II ochre with two elongate and washed blackish median markings and two smaller dark brown markings posterolaterally. Two similar small blackish markings in anterior portion of tergum III. Tergum V with lateral surfaces mostly pale ochre and with a blackish streak in anterior half. Terga VII and VIII each with a dark brown to black central marking. Cerci and epiproct straw. A blackish sub-apical marking also present on interior surface of protibiae. Mesofemora irregularly dark brown basally and with a buff transverse sub-basal band, the mesotibiae buff in the median portion and dark brown apically. Metafemora ochre on their interior surface. Antennae greyish mid brown ventrally, ochre dorsally with most antennomeres dark apically; scapus buff. Eyes dark grey.

Head: Elongate, sub-cylindrical, notably longer than wide and very slightly narrowed posteriorly. Between the eyes with a raised transverse area which has both outer ends protruded into an obtuse, slightly anteriad directed spine. Vertex flattened and irregularly set with granules, nodes and tubercles of variable sizes, also a few tubercles present on genae. Posterior margin with a transverse row of four obtusely rounded but enlarged tubercles. Eyes almost circular in outline, weakly protruding and their diameter contained 2.2x in length of genae.Antennae projecting somewhat over posterior margin of mesothorax. Scapus strongly compressed dorsoventrally, narrowed basally, expanded medially and roughly oval in outline. Pedicellus slightly oval in cross-section and less than half the length of scapus.

Thorax: Pronotum roughly of same dimensions as head, rectangular and 1.7x longer than wide; the transverse median sulcus distinctly impressed but narrow, straight and expanding over entire width of segment. Mesothorax 4.2x longer than pronotum and very weakly widened post-anteriorly. Mesonotum with a fine longitudinal median line and set with a few scattered, enlarged and somewhat wart-like tubercles; a transverse row of four enlarged tubercles just before posterior margin. Metanotum over 3x longer than wide and about 0.6x length of mesonotum, the posterior half weakly expanded and the median line like on mesonotum. Mesopleurae with a medio-longitudinal row of flat, elongate tubercles. Mesosternum densely granulose.

Abdomen: Median segment a little more than half the length of metanotum, 1.8x longer than wide with the lateral margins weakly concave and a small transverse swelling posteromedially. Abdomen excluding median segment slightly shorter than pro-, meso- and metathorax combined with segments V–VI notably swollen. Segment II about equal in length to median segment, II–IV uniform in length and V–VII gradually increasing in length; II parallel-sided and 2x longer than wide, III–V gradually widening with V only 1.3x longer than wide. Anterior portion of VI widest part of abdomen and tergum strongly narrowing towards posterior with a trapezoidal outline; lateral margins somewhat deflexed. VII parallel-sided, as broad as II and but shorter and hardly longer than wide. Tergum II with a transverse posterior lobe that bears five rounded tubercles, V and VI each with a similar but more obtuse transverse posteromedian protuberance. Terga VII and VIII each bear a slightly bilobed posteromedian excrescence, which posteriorly extends over the anterior portion of the following tergum ( Fig. 18E ). Preopercular organ formed by a pair of low and obtuse, verruculose swellings near posterior margin of sternum VII. Tergum IX transverse and slightly narrowed towards the posterior. Anal segment narrower than all preceding segments, weakly keeled medio-longitudinally, almost 2x higher than long and with a widely rounded posteromedian excavation ( Fig. 18F ); the posterolateral angles somewhat protruded and the lateral margins slightly deflexed. Epiproct fairly large, shieldshaped and broadly rounded with an obtuse medio-longitudinal bulge; slightly projecting beyond apex of abdomen ( Fig. 18F ). Cerci small, compressed laterally and gently spiral in their length axis. Subgenital plate bulgy and with a prominent, irregularly dentate median keel in posterior portion; very slightly reaching beyond apex of abdomen ( Fig. 18E ).

Legs: In general shape and anatomy rather typical for the genus. Posteroventral carina of profemora with a big triangular sub-apical tooth followed by a small tooth; the anterodorsal carinae strongly lamellate and weakly undulate. Dorsal carina of protibiae strongly rather unevenly deflexed and lamellate with the apical portion forming an obtuse, roughly triangular lobe; not deflexed in the very basal portion although. Two outer ventral carinae slightly lamellate and unevenly undulate. Mesofemora with a very large lobe that is roundly indented medially and thus is of a general bi-lobed outline; the raised apical portion with an additional tooth ( Fig. 18D ). Posteroventral carina protruded into a moderately sized but fairly acute distal directed tooth at the apex. Two outer ventral carinae each with two triangular sub-apical teeth, the apical one being much smaller than the preceding. Mesotibiae with two almost semi-circular dorsal lobes, one sub-basally and one sub-apically ( Fig. 18D ). Metafemora slender and strongly laterally compressed as usual for the genus; the two outer ventral carinae each with three sub-apical teeth, that decrease in size towards apex of femur. Probasitarsus with a moderately sized roughly triangular dorsal lobe; meso- and metabasitarsus simple and just slightly longer than following tarsomere.

Comments: Males and eggs unknown. Günther (1938: 78) erroneously assigned this specimen to Hermagoras hosei ( Kirby, 1896) , a species endemic to Borneo, and also in error referred to this species as a synonym of Staelonchodes haematomus ( Westwood, 1859) which however is a distinct species that also is an endemic of Borneo. Moreover, Günther (1938: 78) assumed this ♀ was the opposite sex of the ♂ paratype of Hermagoras celebensis ( Hennemann, 1998) n. stat. but examination of the concerned specimen clearly shows it is a distinct species, which for instance is at first glance seen by the morphology of the mesofemora. This latter character is known to be very constant in species of Hermagoras Stål, 1875 and Mnesilochus Stål, 1877 , thus being a useful character for species distinction within these two genera. Careful re-examination of this ♀ has shown it to represent an as yet undescribed species and the lack of a medio-longitudinal keel on the mesosternum places it in the genus Mnesilochus .

Distribution: South Sulawesi, Sulawesi Selatan, Luwu Regency [NHMB].

Figures

FIGURE 18. Mnesilochus luwuense n. sp. ♀, holotype [NHMB]: A. Habitus, dorsal view; B. Habitus, dorso-lateral view; C. Habitus lateral view; D. Right mid leg in postero-lateral aspect; E. Lateral view of terminal abdominal segments; F. Dorsal view of terminal abdominal segments.