Termitotrox shimadai Kakizoe, Hasin & Maruyama, 2025

Termitotrox shimadai Kakizoe, Hasin & Maruyama View in CoL , sp. nov.

( Figs 1–5 View FIGURES 1–5 , 7 View FIGURES 6–9 , 10 View FIGURES 10–13 )

Type material. Holotype, male ( NSMT): Thailand, Nakhon Ratchasima province, Wang Nam Khiao district, Sakaerat Biosphere Reserve , (alt. 530 m), 14.49°N, 101.92°E, 3 VII 2024, S. Kakizoe leg. (from the nests of Odontotermes sp. ) GoogleMaps . Paratypes, 2 females ( DNP, SKC): same data as holotype GoogleMaps ; 1 female ( KUM): same data as holotype GoogleMaps but (alt. 500 m), 2 VII 2024, T. Shimada leg. (from the nests of Microcerotermes sp. ).

Description of holotype, male. General color ( Figs 1–3 View FIGURES 1–5 , 7 View FIGURES 6–9 ) uniformly reddish-brown, matt, body length 1.16 mm. Head ( Figs 1–3 View FIGURES 1–5 ). Surface generally evenly convex, clypeofrontal suture imbricate apart from a slight callosity in the middle (at high magnification). Lateral margins of head entirely, finely marginate. Clypeal outline evenly rounded over entire length. Clypeofrons glabrous, distinctly, moderately punctate. Vertex with elongate deep punctures. Genae obtusely angular (in dorsal view); genal surface depressed, imbricate.Antennae ( Figs 1–3 View FIGURES 1–5 ) yellowish-brown, 9-segmented, including the 3-segmented club. Compound eyes absent. Pronotum ( Figs 1–3 View FIGURES 1–5 ). Prothorax slightly narrower than elytra, sides (in dorsal view) slightly sinuate inwardly. Anterolateral lobes acutely angular (in dorsal view), edge slightly projecting downward (forming side of anterolateral propectoral cavity). Pronotal sides steeply declivous. Posterolateral sections of pronotum rounded. Base of pronotum evenly rounded. Pronotal surface glabrous except for costae. Costae densely punctate, microsetose, intercostal sulci distinctly wrinkled. Central depression deep; surfaces of depression surrounding median costa wrinkled; surfaces of posterior half of central depression imbricate, with elongate deep punctures. Pronotal pattern of longitudinal costae as follows: Median costa at anterior margin broad, becoming indistinct around anterior 1/3. Basomedian section wide, concave, surface imbricate, with elongate deep punctures; forming basomedian protrusion posteriorly; tip of protrusion rounded. Paramedian costae narrow. Sublateral costae anteriorly broad, distinct, tapering posteriad to about 1/3 of pronotal length, reaching paramedian costa. Lateral costae anteriorly broad, distinct, extending from anterolateral lobe caudad, tapering to base of pronotum. Marginal costae anteriorly broad, tapering to base of pronotum. Elytra ( Figs 1–3 View FIGURES 1–5 ). Elytra, semi-spherical, strongly convex dorsally, as high as pronotum, with 9 interstriae and intervening striae, and with short trichomes at base of interstriae 4–6 forming wing-shaped patches. Apicosutural angle nearly rectangular, slightly protruding. Epipleuron wide. Elytral striae distinct, wide, deeply impressed, with transverse weak costae forming quadrate cells present from base to apex. Discal interstrial costae generally broadly trapezoidal (in cross-section), surface with dense, scattered micropunctations, microsetose. Elytral pattern of interstrial costae as follows: interstria 1 (next to suture) tapering in front, stopping at basal 2/3; interstria 2 tapering in front, stopping at basal 2/3; interstria 3 complete, slightly tapering in posterior, weakly protruding in front; interstria 4, 5 and 6 complete, narrow; interstria 7 complete, basally broad, strongly developed; interstria 8 complete, strongly developed; interstriae 9 and 10 apparently fused together. Apterous. Scutellum notably small, invisible in dorsal view. Prosternum ( Fig. 2 View FIGURES 1–5 ). Anterolateral part of propectus deeply excavate. Preprosternal apophysis notably small, invisible in ventral view. Propectus glabrous. Posterolateral areas of propectus imbricate. Postprosternal surface glabrous, imbricate, flattened. Mesoventrite ( Fig. 2 View FIGURES 1–5 ). Surface glabrous, imbricate, flattened, moderately micropunctate in posterior half. Mesoventrite with distinct heart-shaped groove bordering mesocoxae. Metaventrite ( Fig. 2 View FIGURES 1–5 ). Metaventrite glabrous, imbricate, flattened, moderately micropunctate. Abdomen ( Fig. 4 View FIGURES 1–5 ). Venter with 6 fairly sclerotized abdominal ventrites, imbricate, microsetose; abdominal ventrite 2 with series of distinct, short, punctures in middle; abdominal ventrites 3–5 with series of distinct, short, punctures along base at middle; abdominal ventrite 6 with punctures. Pygidium microsetose, generally convex, moderately micropunctate; base broadly marginate. Legs ( Figs 1–3 View FIGURES 1–5 ). Procoxae protuberant. Profemora underside surface microsetose, moderately micropunctate, weakly imbricate; outline broadly elliptical, emarginate distally. Protibiae pale brown, broad, sparsely short setose, microsculpture poorly pronounced; shape strongly complanate with 2 external denticles, no basal serration; apex oblique-sinuate, transverse, with distinct apico-internal spine; internal side strongly dilated from slender base. Protarsi pentamerous, two times longer than width of tibial apex, slender, yellowish brown; segment 1 inserted in fine groove, as long as segments 2–4 combined. Anterior claws normal, symmetrical. Mesocoxae widely separated, slightly divergent anteriad. Mesofemora broadly elliptic in outline, surface moderately micropunctate, microsetose, imbricate. Mesotibiae with several setae, broad, abruptly dilated near base, nearly parallel-sided from apex, edges entire; tibial apex slightly emarginate, with pair of acuminate apico-internal spurs, external one long, slightly curved, internal one short, straight; upper side of mesotibia with fine longitudinal ridge near outer edge, underside with two fine sinuate ridges from base to apico-internal section; with long setae around apical half. Metatibiae similar to mesotibiae, but shorter and gently dilated apically, with apex shallowly emarginate. Meso- and metatarsi pentamerous, reddish brown, compacted-complanate, segments 1–4 short. Length of outer apical spur of metatibia 1/4 length of metatibia, reaching base of tarsal segment 5. Middle and hind claws normal, symmetrical. Aedeagus ( Fig. 5 View FIGURES 1–5 ). Symmetrical, length of aedeagus 0.59 mm (50.9 % of body length). Phallobase elongate, cylindrical. Parameres short, weakly sclerotized inwardly, almost half-length of basal piece. Apophyses of parameres long, almost same length of phallobase. Median lobe with long apophyses (temones) almost same length of phallobase; anterior angle acute.

Female. Secondary sexual dimorphism not appreciable.

Measurements (n=2). Body length 1.16–1.20 mm; maximum width of head 0.49–0.51 mm; median dorsal length of pronotum 0.45–0.47 mm; maximum width 0.52–0.54 mm; sutural length of elytra 0.47–0.49 mm; maximum width 0.62–0.64 mm.

Differential diagnosis. This species is similar to Termitotrox cupido Maruyama, 2012 ( Fig. 12 View FIGURES 10–13 ) in size ( 1.2 mm) and in having wing-shaped trichomes at the base of the elytra, but is easily distinguished by a combination of the following characteristics: a) the basomedian protrusion of the pronotum is rounded at the tip (serrate in T. cupido ), b) the elytral striae are deeper and distinctly wider than those of interstriae 4, 5, and 6 (shallow in T. cupido and almost as wide as those of interstriae 4, 5, and 6), and c) in the heart-shaped groove in mesoventrite, the two nearly parallel grooves are not close together in the center (in T. cupido , the two grooves are in contact).

Distribution. Central Thailand.

Etymology. This species is named in honor of its first discoverer, Mr. Taku Shimada, who has made outstanding observations and discoveries on ants and symphilic insects.

Symbiotic host. Odontotermes sp. (identified by Dr. Yoko Takematsu).

Behavioral observations. In laboratory-based observations, we observed multiple instances of host termite minor workers carrying T. shimadai sp. nov. individuals with their mandibles ( Figs 8, 9 View FIGURES 6–9 ). Nutrient exchange (trophallaxis) between the termite and beetle was not observed during either field or laboratory observations.

Termitotrox shimadai View in CoL sp. nov. has wing-shaped trichomes on the elytra, a characteristic shared with three previously known species from the Indo-Chinese subregion: T. cupido Maruyama 2012 View in CoL and T. venus Kakizoe & Maruyama 2015 View in CoL from Cambodia, and T. icarus Kakizoe, Liang & Maruyama, 2020 View in CoL from Myanmar ( Figs 10–13 View FIGURES 10–13 ). That suggesting a close phylogenetic relationship among these species.

Host-carrying behavior, in which minor workers of Odontotermes View in CoL transport beetles using their mandibles ( Fig. 9 View FIGURES 6–9 ), was observed in the laboratory. This behavior, also reported in T. icarus View in CoL and T. cupido ( Kakizoe et al. 2020) View in CoL , may be facilitated by the presence of wing-shaped trichomes, indicating a possible morphological adaptation for symbiotic interaction. Although we were unable to take clear photographs such as figures 18 and 19 in Kakizoe et al. (2020) due to limited observation time in the laboratory, the way in which the host termite held T. shimadai View in CoL sp. nov. was similar to that of T. icarus View in CoL shown in Kakizoe et al. (2020).

Prior to this study, Termitotrox was known from India, Cambodia, and Myanmar in the Oriental region. As anticipated by Kakizoe et al. (2020), this research confirms the presence of the genus in Thailand, thereby expanding its known distribution. This finding underscores the incomplete understanding of termitophilous insect diversity in Southeast Asia. Continued exploration of termite nests and other specialized microhabitats is likely to reveal additional undescribed species.

Although numerous Macrotermitinae termite species are present in the Sakaerat area ( Inoue et al. 2001), T. shimadai sp. nov. was found exclusively in nests of Odontotermes . This contrasts with findings from Siem Reap, Cambodia, where other Termitotrox species were associated with Hypotermes and Macrotermes ( Maruyama 2012; Kakizoe & Maruyama 2015). While we caution against overinterpretation due to the short duration of the survey, this pattern may reflect regional differences in host usage. Such variation could be crucial for understanding the evolutionary dynamics of host specificity and shifts within Termitotrox lineages.