Eufalconius sekayu Muhammad, Azizan, Abdullah & Tan, 2025

Eufalconius sekayu Muhammad, Azizan, Abdullah & Tan , sp. nov.

( Figs 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. Holotype: PENINSULAR MALAYSIA • ♂; Terengganu; Kuala Berang, Sekayu ; N4.972248 E102.957732, 71.8 m.a.s.l.; 9 October 2024, 09h52; on tree trunk by the stream; coll. A.A. Muhammad, I.A. Azizan, N.A. Abdullah; HSHTT2024.072 ( MZUM). GoogleMaps

Paratypes: PENINSULAR MALAYSIA, Terengganu; Kuala Berang, Sekayu • 1♀; same details as holotype; HSHTT2024.073 ( MZUM) • 1♀; N5.404294 E103.094816, 116 m. a.s.l.; 9 October 2024, 21h35; on fallen tree trunk along trail; coll. A.A. Muhammad, I.A. Azizan, N.A. Abdullah; HSHTT2024.082 ( MZUM) GoogleMaps • 1♀; N5.404294 E103.094816, 116 m. a.s.l.; 9 October 2024, 21h35; on fallen tree trunk along trail; coll. A.A. Muhammad, I.A. Azizan, N.A. Abdullah; HSHTT2024.083 ( ZRC) GoogleMaps .

Generic status. We place the new species under Eufalconius Günther, 1938 due to the similarities with the type species Eufalconius pendleburyi Günther, 1938 (see diagnosis), which was described from Pahang, Peninsular Malaysia.

Diagnosis. From type species Eufalconius pendleburyi Günther, 1938 , the new species differs by its pronotum slender [smaller pronotal width (PnW = 4.16±0.18 vs. 5.86± 0.21 mm); prozonal width smaller (PrzW = 1.12±0.05 vs. 1.27± 0.12 mm)]; its lateral lobe curve outwards, forming an acute apex; the hindwings visible from lateral view and reaching or slightly surpassing the apex of pronotum (hWL = 8.69± 0.22 mm); the 12 th antennal segment with its basal half white in color; the lateral ocelli at the lower half of the compound eyes height; its tegmen longer and wider (TL = 1.50±0.14 vs. 1.33± 0.06 mm; TW = 0.66±0.13 vs. 0.52± 0.10 mm); its fore, mid, and hind femora shorter and slender (fFL = 2.77±0.21 vs. 3.11± 0.04 mm; fFW = 0.63±0.04 vs. 0.77± 0.01 mm; mFL = 3.22±0.32 vs. 3.33± 0.61 mm; mFW = 0.79±0.03 vs. 0.78± 0.02 mm; hFL = 6.42±0.20 vs. 6.91± 0.06 mm; hFW = 2.15±0.38 vs. 2.66± 0.01 mm).

Etymology. This species is named after the type locality Sekayu in Kuala Berang, Terengganu, Peninsular Malaysia; noun in apposition.

Description. Male. Body of moderate size (BL = 10.03 mm) and robust ( Fig. 1 View FIGURE 1 ). Body dark brown with speckles of lighter brown.

Head. In frontal view ( Figs 2A, 2B View FIGURE 2 ): head rugose. Face dark brown with speckles of light brown ( Fig. 2A View FIGURE 2 ). Vertex with transverse and lateral carinae faintly elevated, not elevated above dorsal margin of compound eyes ( Fig. 2A View FIGURE 2 ). Frontal costa bifurcates below middle of compound eye height, just between paired lateral ocelli ( Fig. 2A View FIGURE 2 ). Lateral ocelli at lower half of the compound eyes height ( Fig. 2A View FIGURE 2 ). Scutellum in its widest part 1.5 times wider than antennal groove ( Fig. 2A View FIGURE 2 ). Scutellum forms shallow concavity, widens ventrally ( Fig. 2A View FIGURE 2 ). Antennae filiform, 13- segmented ( Fig. 2B View FIGURE 2 ); antennal grooves below level of lower margin of eyes ( Fig. 2A View FIGURE 2 ); ScW/SW = 0.10. Antennal segment dark brown with lighter brown towards apex ( Fig. 2B View FIGURE 2 ). Longest (9 th) antennal segments 18 times as long as wide (AsL = 0.92 mm; AsW = 0.05 mm) ( Fig. 2B View FIGURE 2 ). Median ocellus ventrad of antennal grooves ( Fig. 2A View FIGURE 2 ). Compound eyes oblongly ovoid, generally dark brown ( Fig. 2A View FIGURE 2 ). Mouth parts mostly light colored; maxillary palps with segments white ( Fig. 2A View FIGURE 2 ). In dorsal view ( Fig. 2C View FIGURE 2 ): Fastigium of vertex with deep concavities behind lateral carinae, not produced in front of eyes ( Fig. 2C View FIGURE 2 ), EW/VW = 0.40. Fastigium with anterior margin truncated, median carina not produced in front of anterior margin of fastigium; lateral carinae elevated; subocular lobes distinct ( Fig. 2C View FIGURE 2 ). Compound eyes oval ( Fig. 2C View FIGURE 2 ). In lateral view ( Fig. 2D View FIGURE 2 ): Compound eyes hemispheric, not exerted above vertex ( Fig. 2D View FIGURE 2 ). Frontal ridge (or scutellum) distinctively produced to form two broadly rounded lobes; the two lobes of about equal height ( Fig. 2D View FIGURE 2 ). Genae dark brown ( Fig. 2D View FIGURE 2 ).

Pronotum. Robustly rugose, surpassing abdominal apex and hind femur ( Fig. 1 View FIGURE 1 ). In dorsal view ( Fig. 1 View FIGURE 1 , 2C View FIGURE 2 ): lateral lobe with anterior margin notched, forming acute apex and pointing anteriorly outwards ( Fig. 2C View FIGURE 2 ). Hind margin almost straight at an obtuse angle ( Fig. 1 View FIGURE 1 ). Margins of lateral lobes light colored ( Fig. 2C View FIGURE 2 ). In lateral view ( Figs 1 View FIGURE 1 , 2D, 2E View FIGURE 2 ): Prozonal carinae well defined ( Fig. 1 View FIGURE 1 ). Pronotum disc with both sides of median carina having numerous net-like elevations ( Fig. 1 View FIGURE 1 ). Medium-sized PM, large MM1, and small MM2 unpaired medial projections ( Fig. 2D View FIGURE 2 ); three pairs of small (PML1, PML2 and MML1) projections, two pairs of large mediolateral (MML2, MML3) projections, and 4–5 pairs of small hardly recognizable tubercles situated posteriorly to MML3 projection ( Fig. 2D View FIGURE 2 ); two pairs of hardly recognizable (PL1, PL2) tubercles, one pair of ML and one pair of VL projections ( Fig. 2D View FIGURE 2 ). Between anterior sides of humero-apical carinae (on both sides of MM1 projection, and behind PML2 projection) with largest paired depressions; with small depressions present on apical part of shoulder, on both sides of small MML1 projection (top of hardly recognizable carina, beginning from MM1 and situated at about 45 degrees to median carina) ( Fig. 2D View FIGURE 2 ). MML3 projection (located on both sides of pronotum, somewhat before midlength of hind femur) large and oblique ( Fig. 2E View FIGURE 2 ). At same line behind MML3 projection in direction to apex of posterior pronotal process with about 4–5 smaller hardly recognizable tubercles ( Fig. 2E View FIGURE 2 ).

Wings. Tegmen elongated, oval with apical margin obtuse or subacute; TL/TW = 2.25 ( Fig. 2F View FIGURE 2 ). Hind wings long, reaching or slightly surpassing apex of pronotum ( Fig. 1 View FIGURE 1 ).

Legs. Fore and mid femora compressed laterally ( Fig. 2C View FIGURE 2 ). Carinae of fore femur equipped with a pair of strong teeth on both upper and lower sides ( Fig. 2C View FIGURE 2 ). Carinae of mid femur equipped with three strong teeth on upper side and two on lower side ( Fig. 2C View FIGURE 2 ). Mid femur with upper margin tapered into acute apex ( Figs. 2D, 2E View FIGURE 2 ). Fore and mid femora dark brown, with speckles of light brown ( Figs. 2D, 2E View FIGURE 2 ). Fore and mid tibiae dark brown with three light brown rings each ( Fig. 2C View FIGURE 2 ). Fore and mid tarsi, with first segment dark brown, and third segment dark brown with a light brown ring ( Fig. 2C View FIGURE 2 ). Hind femur dark brown with basal third light brown, and at middle having one light brown tubercle, 3.06 times as long as wide ( Fig. 2E View FIGURE 2 ). Hind femur with upper and lower margins finely serrated ( Fig. 2E View FIGURE 2 ). Hind tibia dark brown with two light brown rings, not widened ( Fig. 2G View FIGURE 2 ). Hind tibia with upper side serrated with 18–22 small teeth on the inner and outer margins ( Fig. 2G View FIGURE 2 ). First tarsal segment with ventral surface having 3 pads, with 1 st pad reduced in size; 2 nd and 3 rd pads of equal size. Length of first tarsal segment of hind legs 1.37 times length of third segment (without claws) ( Fig. 2G View FIGURE 2 ). Hind tarsus with first segment dark brown, distal half light brown including tarsal pads; second segment light brown, third segment white except at apex ( Fig. 2G View FIGURE 2 ).

Abdominal apex. Tergite generally dark brown; sternites, including subgenital plate generally brown with speckles of light brown ( Fig. 2H View FIGURE 2 ). Subgenital plate in ventral view triangular, with apex of plate slightly excised; in lateral view slender and elongated ( Fig. 2H View FIGURE 2 ). Cercus stout basally with pointed apex ( Fig. 2H View FIGURE 2 ).

Female. Similar to male, but larger (BL = 12.52± 0.07 mm) ( Fig. 1 View FIGURE 1 ). Body, head, and legs generally similar colored ( Figs. 1 View FIGURE 1 , 4 View FIGURE 4 ). Longest (9 th) antennal segments 16–20 times as long as wide (AsL = 0.75± 0.02 mm; AsW = 0.04±0.00 mm) ( Table 1). EW/VW = 0.47±0.03 ( Table 1). Length of first tarsal segment of hind legs 1.5 times as long as that of third segment (without claws) ( Table 1). TL/TW = 2.12±0.13 ( Table 1). Subgenital plate 1.73 times longer than broad, OvL/OvW = 1.73±0.07 ( Table 1). Posterior margin of subgenital plate at middle with small nodule ( Fig. 2I View FIGURE 2 ). Cerci same as male ( Fig 2H, I View FIGURE 2 ). Valves of ovipositor narrow and serrated ( Fig. 2I View FIGURE 2 ). Ovipositor dark brown with speckles of light brown, with apices of denticles blackish ( Fig. 2I View FIGURE 2 ).

Distribution. This new species was first found in Sekayu, Terengganu, which is not part of the Titiwangsa Mountain range, where E. pendleburyi was mostly collected.

Remarks. We observed three color forms of this species: unicolorous dark brown ( Figs 1A View FIGURE 1 , 4B View FIGURE 4 ), ML plate dark brown with lighter margins ( Fig. 1C View FIGURE 1 ), and dark-brown with lighter horizontal band across ML plate ( Fig. 4A View FIGURE 4 ). It is postulated that these color variation helps with camouflage, as E. pendleburyi may also display color variations ( Cigliano et al., 2025).