Tisamenus trapezoides, Hennemann, 2025

Hennemann, Frank H., 2025, A taxonomic review of Philippine Obrimini stick insects: The genus Tisamenus Stål, 1875 (Insecta: Phasmatodea: Heteropterygidae: Obriminae), Faunitaxys 13 (24), pp. 1-85 : 75-77

Tisamenus trapezoides n. sp.

( Fig. 44-45)

ZooBank: https://zoobank.org/ 2B9AFCA0-BEB1-42CB-A05B-2E483B30E221

HT, ♀: Coll. R.I.Sc.N.B., Philippines, E Luzon, Quirino, Sierra Madre , ii.2014, Purchased from I. Lumawig, Gift from B. Kneubühler,I.G.: 32.613 [ RBINS] .

PT, 1 ♀, 1 ♂: Coll. R.I.Sc.N.B., Philippines, E Luzon, Quirino, Sierra Madre , ii.2014, Purchased from I. Lumawig, Gift from B. Kneubühler, I.G.: 32.613 [ RBINS] .

Differentiation. – Females of this remarkable new species ( Fig. 44 A-C) are morphologically very close to those of T. ranarius (Westwood, 1859) but easily separable by the more distinctly widening meso- and metathorax, more tubercular lateral margins of the meso- and metapleurae as well as the larger and sub-spinose metapleural (obtuse and tuberculate in ranarius ), notably larger, conical sub-orbitals, more distinct triangular area of the pronotum ( Fig. 44G), much more pronounced medio-longitudinal keel of the dorsal body surface, comparatively weaker indicated longitudinal carinae of the mesosternum ( Fig. 44H), considerably more developed armature of the limbs(metafemora in particular) and contrastive ochre to clay coloured tibiae. The dentiform apical protrusion on the exterior lateral carina od the scapus ( Fig. 44 G-H), remarkably reduced and almost indiscernible triangular mesonotal area ( Fig. 44G) and sub-spiniform postero-laterals of the abdominal terga are shared with ranarius and all three features are likely to represent autapomorphies of these two species, which presumable represent sister taxa.The ♂ of ranarius are not known, but if compared to other congenerics these ♂ are morphologically closest to T. deplanatus ( Westwood, 1848) and T. cervicornis Bolívar, 1890 but in addition to the characteristics shared with ranarius and mentioned above, may be distinguished from both species by the smaller size, more conical and stronger supra-orbitals, lack of an enlarged mesopleural, lack of paired posteriors on the abdominal terga and much smaller pronotal anterior, which is merely represented as a moderately sized simple spine ( Fig. 45H; much larger and bi- or trifid in deplanatus and cervicornis ).

Etymology. – The name of this very distinctive new species refers to the characteristic shape of the meso- and metathorax, which are strongly and uniformly widening towards the posterior and together form a trapeziform unit.Adjective.

A. Dorsal view. B. Dorsolateral view. C. Ventral view. D. Terminalia in lateral view. E. Terminalia in dorsal view. F. Terminalia in ventral view. G. Closeup of head, pro- and mesonotum (arrows pointing the dentiform apical protrusion on the exterior lateral carina of the scapus and strongly reduced triangular mesonotal area). H. Closeup of head, pro- and mesosternum (arrow pointing to the dentiform apical protrusion on the exterior lateral carina of the scapus).

Description

♀ ( Fig. 44)

Form and colouration. – Small for the genus (body length 44.2-44.8 mm); general form heavy with meso- and metathorax strongly and uniformly widening towards the posterior to form a distinct trapeziform unit ( Fig. 44A); elements of armature weakly developed and body surface unevenly granular; legs short and moderately stocky. General colour buff to reddish fuscous dorsally, the ventral body surface with a slight buff to walnut brown hue; largest spines of head, thorax and limbs tipped with orange. Femora dark brown, tibiae contrastive ochre to clay coloured. Four terminal antennomeres straw coloured, the preceding gradually becoming brown towards scapus.

Head. – Roundly sub-quadrate, scarcely longer than wide with the genae roughly parallel-sided; coronal line and lateral furrow of vertex notably indented. Supra-orbitals prominent, triangular, laterally compressed and together with an anterior and posterior tubercle forming a crest-like element that is anteriorly extended into a shallow bulge that attains the bases of the antennae; occipitals and coronals rather low, rounded tuberculate; two gulars small and nodose ( Fig. 44G). Eyes small, sub-globose and their diameter corresponding to a little less than half the length of gena. Antennae strong, reachingtotip of protarsi and consistingof 26joints, the basalhalf of antennae except three basal joints perlamorph in appearance; scapus somewhat narrowing towards base with exterior lateral margin apically protruded into an obtusedentiform protrusion;pedicelluslessthanhalf aslong as scapus, barrel-shaped; III notably shorter, IV-VIII transverse and up to XIX gradually increasing in length; terminal antennomere somewhat elongated and slightly longer than preceding joint.

Thorax. – Pronotum sub-trapeziform; triangular area fairly distinct with margins shallowly tubercular and the anterolateral angles with a strong and slightly backward arched spine; the four tubercles directly in front and behind the transverse median sulcus somewhat enlarged, obtuse; antero-lateral low, tubercular ( Fig. 44G). Mesothorax trapeziform, distinctly, gradually and uniformly widening towards posterior, almost 2.0x longer than prothorax and with posterior portion almost 1.7x wider than anterior margin. Mesonotum sub-rectangular in outline with a distinct concave post-medial constriction; about 1.7x longer than width at anterior margin; over entire length with a distinct, granular medio-longitudinal ridge, the triangular area very small and merely represented by three low granules at anterior margin of notum that are arranged in a triangle ( Fig. 44G). Mesopleurae strongly expanded and widening towards the posterior, triangular in dorsal aspect, the laterals margins denselybut somewhat unevenlytubercular; mesopleural missing. Metanotum slightly transverse with a distinct pre-mediannarrowing and the same medio-longitudinal keel seen on mesonotum. Metapleurae basically like mesopleurae, strongly expanded but the supra-coxal angle with a prominent, strong but blunt and sub-spiniform metapleural; supra-coxal very small, low and nodose. Prosternal sensory-areas well developed; probasisternum with a transverse row of four low nodes, the exterior ones of which are more pronounced. Mesosternum weakly tri-carinate with the lateral carinae less pronounced and supplied with 2-3 low nodes anteriorly; metasternum only with a faint indication of a medio-longitudinal carina ( Fig. 44H).

Abdomen. – Median segment distinctly transverse, roughly pentagonal and obtusely keeled medio-longitudinally. Segments II-VII all distinctly transverse, slightly decreasing in length and on average about 3x wider than long; IV-X slightly but almost gradually narrowing. Terga all with a distinct medio-longitudinal carina which is posteriorly terminating in swelling, that is sub-obsolete on II, nodose on II-V and dentiform, on VI-VIII and forms a tectate swelling on IX that covers almost the whole dorsal surface of tergum ( Fig. 44D); first and second paired posteriors merely represented as small granules; postero-laterals distinct and sub-spinose on II-IV. Sterna II-VI rather smooth with a shallow medio-longitudinal keel; II with a distinct roundly rectangular, transverse indention antero-medially; VII with a pair of low, converging bulges that terminate in an obtuse swelling posteriorly. Anal segment weakly trapezoidal in outline and strongly declining; the lateral margins obliquely convergent in posterior half and protruded into an obtuse tooth at the angle; the posterior margin weakly rounded with outer angles somewhat protruded ( Fig. 44E). Epiproct convex with a faint indication of a medio-longitudinal carina, gradually convergent and the apex flattened and obtusely rounded ( Fig. 44E). Subgenital plate navicular, carinate apically and progressively narrowing towards a rather pointed apex, that scarcely surpasses the epiproct ( Fig. 44F).

Legs. – Moderately stocky with only the ventral femoral teeth notably developed, only dorsal carina of metafemora with two upright basal spines on posterior carina, of which the basal spine is much larger than the rather tubercular second one. Pro- and mesofemora somewhat shorter than mesothorax, metafemora reaching halfway along abdominal segment V and metatibiae almost attaining anal segment. Two ventral carinae of mesofemora with four blunt teeth that increase in size towards apex of femur; dorsal carinae only with some low swellings. The five ventral teeth of metafemora prominent, obtusely spiniform and becoming stronger towards apex of femur. Pro- and mesotibiae wholly unarmed; metatibiae only with 5-6 faint indications of teeth on two ventral carinae. Basitarsi short and no longer than following two tarsomeres combined.

Measurements of holotype [mm]. – Body44.2,pronotum4.1,mesonotum 8.5, metanotum 4.3, median segment 2.3, profemora 7.8, mesofemora 6.5, metafemora 8.1, protibiae 6.8, mesotibiae 6.4, metatibiae 9.0, antennae 11.0.

Measurements of paratype [mm]. – Body44.8,pronotum 4.1,mesonotum 8.6, metanotum 4.3, median segment 2.3, profemora 7.5, mesofemora 6.8, metafemora 8.7, protibiae 7.0, mesotibiae 6.2, metatibiae 9.1, antennae 11.5.

♂ ( Fig. 45)

Form and colouration. – Size small (body length 32.8 mm); general form relatively slender, legs fairly strong with the metafemora incrassate; elements of armature weakly developed, essentially as in ♀ but cephalic and prothoracic elements as well as the metapleural supra-coxal comparatively more prominent; the second paired posteriors seen on terga II-IV of ♀ missing and the posteromedian protrusion of abdominal terga VII-IX less distinct. Meso- and metathorax less than in ♀, but notably gradually widening towards posterior and together forming a trapeziform unit; body surface unevenly granular. Colour basically as in ♀.

Head. – As in ♀ but with the supra-orbitals and coronals more pronounced.

Antennae only with 24 joints ( Fig.45H).

Thorax. – Pronotum like in ♀ but the anteriors more spiniform ( Fig. 45H). Mesothorax gradually widening towards posterior, about 1.8x longer than prothorax and with posterior portion almost 1.4x wider than anterior margin. Mesonotum elongate withlateralmargins weaklyconvergent towards the posterior and with a distinct concave post-medial constriction; about 2.x longer than width at anterior margin; over entire lengthwith a granular medio-longitudinal ridge that is weakly gibbose posteriorly; the triangular area very small and merely represented by three low granules at anterior margin of notum that are arranged in a triangle ( Fig. 45H). Mesopleurae strongly expanding towards the posterior, triangular in dorsal aspect, the laterals margins merely sub-tubercular and without any enlarged tubercles; mesopleural missing. Metanotum roughly rectangular with a distinct median narrowing and the same medio-longitudinal keel seen on mesonotum; posterior portion weakly gibbose. Metapleurae basically like mesopleurae but the supra-coxalangle witha prominent, strong butblunt supra-coxaltubercle; metapleural lowandnodose.Mesosternum weakly tri-carinate with the lateral carinae less pronounced and somewhat irregular ( Fig. 45I); metasternum only with a faintly indicated medio-longitudinal carina in anterior portion.

Abdomen. – Median segment distinctly transverse and roundly pentagonal, surface weakly carinate medio-longitudinally. Segments II-VII slightly sub-uniform in length and width, II-III very gentlynarrowing and V-VII indistinctly decreasing in length; II sub-trapeziform and IV about 1.6x wider than long. All terga with a shallow but bold medio-longitudinal bulge that is most prominent on three terminal terga and comparatively more acute and raised on anal segment; on IX posteriorly terminating in a low, obtuse swelling ( Fig. 45D). Second paired posterior merely represented as very low, sub-obsolete nodes on II and III. Sterna II-VI weakly tri-carinate, VII and VIII bi-carinate. Anal segment moderately declining, trapezoidal in outline and narrowed posteriorly with the lateral margins obliquely angular; posterior margin with a wide and very shallow, angular median emargination and the outer angles obtusely rounded ( Fig. 45E). Epiproct slightly transverse, rounded, scale-like and notably projecting beyond posterolateral protrusions of anal segment ( Fig. 45E). Poculum roundly cup-shaped with a very broad and rounded, labiate posterior flange of the free upper margin, that is minutely and narrowly indented medially and reaches about halfway along anal segment ( Fig. 45F).

Legs. – Moderately stocky with only the ventral femoral teeth notably developed; armature essentially as in ♀ but femora much more incrassate. Pro- and mesofemora noticeably shorter than mesothorax, metafemora reaching halfway along abdominal segment IV and metatibiae almost attaining anal segment. The four ventral teeth of metafemora prominent, obtusely spiniform and becoming stronger towards apex of femur; ventro-basal swelling of metafemora rather shallow and smooth ( Fig. 45G). Pro- and mesotibiae wholly unarmed; metatibiae only with 3-6 faint indications of teeth on two ventralcarinae ( Fig. 45G). Basitarsishortandno longer thanfollowing two tarsomeres taken together.

Measurements of paratype [mm]. – Body32.8,pronotum 3.5,mesonotum 6.8, metanotum 3.4, median segment 1.8, profemora 5.2, mesofemora 4.9, metafemora 5.9, protibiae 5.1, mesotibiae 4.8, metatibiae 5.8, antennae 8.9.

Variability. – No noteworthy morphological variability is seen in the three type-specimens.

Distribution. – Luzon: Province Quirino, Sierra Madre [RBINS].