Carebara eguchii Matsuura & Hosoishi, 2025

Matsuura, Kohei, Hosoishi, Shingo & Pham, Hong Thai, 2025, Taxonomic revision of the Carebara oni species group, with descriptions of two new species from Vietnam (Hymenoptera, Formicidae, Myrmicinae), Deutsche Entomologische Zeitschrift 72 (2), pp. 377-393 : 377-393

Carebara eguchii Matsuura & Hosoishi sp. nov.

Fig. 6 A – F

Type material examined.

Holotype: Vietnam • major worker; Lai Chau, Western slope of Mt. Phansipan ( W. Cong Troi); 2100–2200 m alt.; 6. May 2002; K. Eguchi leg.; colony Eg 02-VN-316 ; VNMN, collection code KUECCRB 011 . Paratypes: Vietnam • 2 major workers and 2 minor workers; Lai Chau, Western slope of Mt. Phansipan ( W. Cong Troi); 2100–2200 m alt.; 6. May 2002; K. Eguchi leg.; colony Eg 02-VN-316 ; KUEC, collection codes KUECCRB 012 , 013; SKYC, collection codes KUECCRB 014 , 015 .

Diagnosis of worker.

Major worker: Dorsal surface of promesonotum reticulate. Lateral surface of pronotum largely reticulate. Reticulation on dorsal surface of propodeum distinct. Subpetiolar process blunt. Minor worker: Vertex reticulate. Dorsal surface of pronotum reticulate. Lateral propodeum reticulate. Propodeal spiracles not tangent to propodeal declivity. Dorsal surface of petiolar node reticulate. Subpetiolar process absent.

Measurements

(in mm) and indices. Holotype (Major worker): TL 3.12, HL 0.87, HW 0.83, SL 0.41, EL 0.07, ML 0.96, MW 0.53, PSL 0.12, PSD 0.04, PL 0.39, PH 0.25, DPW 0.21, PPL 0.22, CI 95, SI 47, PI 1 154, PI 2 54. Paratypes (Major worker, n = 2): TL 2.94–3.00, HL 0.81–0.86, HW 0.77–0.79, SL 0.39–0.41, EL 0.07–0.08, ML 0.88–0.90, MW 0.46–0.50, PSL 0.13–0.15, PSD 0.04, PL 0.35–0.37, PH 0.22–0.24, DPW 0.17–0.18, PPL 0.20–0.21, CI 92–94, SI 48, PI 1 156–157, PI 2 49–50. Paratypes (Minor worker, n = 2): TL 1.86–1.91, HL 0.52, HW 0.51, SL 0.32, EL 0.03, ML 0.56, MW 0.30, PSL 0.07–0.08, PSD 0.03, PL 0.23, PH 0.14–0.15, DPW 0.11–0.12, PPL 0.12–0.13, CI 98, SI 60–61, PI 1 157–161, PI 2 50–51.

Description of worker.

Worker caste dimorphic.

Major worker.

(Fig. 6 A – C ).

Head in full-face view subsquare ( CI 92–95); posterior cephalic border slightly concave in middle; posterolateral corners rounded; lateral margins slightly convex. Anterior clypeal margin concave in middle, with a pair of blunt protrusions. Frontal carinae present. Frontal triangle well-defined. Mandibles short, subtriangular, masticatory margins with six teeth that gradually decrease in size toward mandibular base. One median ocellus and two lateral ocelli present; in other specimen, ocelli absent or one median ocellus and one lateral ocellus present. Eyes with two or three ommatidia, situated at anterior one-third of head, laterally. Antennae with nine segments, with a two-segmented club; scapes narrower than eyes, clavate and slightly shorter than half of head length ( SI 47–48); antennal segment II, VIII, and IX longer than wide, III – VII wider than long.

Mesosoma slightly longer than head ( HL 0.81–0.87, ML 0.88–0.96). Promesonotum roundly convex and higher than propodeum in profile view; anterior and lateral margins of promesonotum convex in dorsal view; promesonotal suture distinct, distinctly or weakly convex forward in dorsal view. Dorsal outline of mesonotum concave in profile view; scutellum present. Mesopleuron separated by transverse striae. Metanotal groove present; metanotum present as elevated band. Dorsal outline of propodeum declining backwards; propodeal spiracle large ( PSD 0.04) and rounded, situated above mid-height of propodeum and at mid-length of propodeum; propodeal spines blunt, short ( PSL 0.12–0.15).

Petiole longer than high ( PI 1 154–157), with short peduncle and high node, broader posteriorly in dorsal view; ventral outline concave; subpetiolar process blunt. Postpetiole as long as high, shorter than petiole, lower than petiolar node in profile view; in dorsal view, postpetiole trapezoidal, wider than petiolar width. Gastral tergite I larger than remaining segments.

Frons with longitudinal irregular rugulae; vertex weakly areolate. Clypeus smooth and shiny medially, lateral sides longitudinally striated. Frontal triangle smooth and shiny. Frontal lobes longitudinally striated. Mandibles smooth and shiny. Cervical shield reticulate. Pronotum largely reticulate, partly smooth and shiny. Mesonotum reticulate anteriorly, remainder smooth and shiny. Scutellum smooth and shiny. Upper portion of mesopleuron partly smooth and shiny, remainder wrinkled and reticulate; lower portion of mesopleuron reticulate. Metapleuron reticulate and wrinkled. Propodeum reticulate. Legs smooth and shiny. Petiole reticulate. Disc of postpetiole smooth and shiny. Gastral tergite I smooth and shiny.

Head dorsally with abundant short decumbent and long erect hairs; vertex with short decumbent hairs. Anterior median clypeus with 2 pairs of long erect hairs. Mandibles, masticatory margins with long decumbent hairs; surface with short decumbent hairs. Antennal scapes with dense short decumbent hairs. Mesosoma with short decumbent and long erect hairs. Legs with short decumbent hairs. Petiolar node and postpetiole with long erect hairs. Gastral tergite I with short decumbent and sparsely long hairs.

Head, antennae, mesosoma, waist, gaster brown. Legs yellowish brown.

Minor worker. (Fig. 6 D – F ).

Head in full-face view almost as wide as long, subsquare ( CI 98); posterior cephalic border almost straight; posterolateral corners rounded; lateral margins convex. Anterior clypeal margin concave in middle, with a pair of acute protrusions. Frontal carinae present. Frontal triangle well-defined. Mandibles short, subtriangular; masticatory margins with six teeth. Eyes with two ommatidia, situated at anterior one-third of lateral head. Antennae with nine segments, with a two-segmented club; scapes wider than eyes, clavate and longer than half of head length ( SI 60–61); antennal segment II, VIII, and IX longer than wide, III – VII wider than long.

Mesosoma almost same size as head ( HL 0.52, ML 0.56). Promesonotum roundly convex and higher than propodeum in profile view; in dorsal view, anterior margin convex forward and lateral margins converging posteriorly; promesonotal suture indistinct. Mesopleuron not separated by transverse striae. Metanotal groove present. Dorsal outline of propodeum declining backwards; propodeal spiracle large ( PSD 0.03), and rounded, situated above mid-height of propodeum and beyond mid-length of propodeum; propodeal spine acute, short ( PSL 0.07–0.08); propodeal lamella thin in upper part, thick in lower part in profile view.

Petiole longer than high ( PI 1 157–161), with short peduncle and low node in profile view; dorsal outline between peduncle and node weakly curved in profile view; in dorsal view, broader posteriorly; ventral outline slightly concave; subpetiolar process absent. In profile view, postpetiole shorter than petiole, lower than petiolar node; dorsal outline convex and ventral outline convex; in dorsal view, subrectangular, wider than petiolar width. Gastral tergite I larger than remaining segments.

Dorsal surface of head largely reticulate, only anterior part of frons longitudinally rugose. Clypeus smooth and shiny medially, lateral sides longitudinally striated. Frontal triangle smooth and shiny. Frontal lobes longitudinally striated. Mandibles smooth and shiny. Antennal scapes smooth and shiny. Cervical shield reticulate. Pronotum, mesonotum, mesopleuron and propodeum reticulate. Legs smooth and shiny. Petiole reticulate. Disc of postpetiole smooth and shiny. Gastral tergite I smooth and shiny.

Dorsal surface of head with short decumbent hairs and long erect hairs; vertex with short decumbent hairs. Anterior median clypeus with two pairs of long erect hairs. Mandibles, masticatory margins with long decumbent hairs; surface with short decumbent hairs. Antennal scapes with dense short decumbent hairs. Mesosoma with short decumbent hairs and long erect hairs; promesonotum with four pairs of long erect hairs, three of them situated at pronotum, one of them situated at mesonotum; propodeum with a pair of long erect hairs, situated at middle of dorsal outline of propodeum. Legs with short decumbent hairs. Petiolar node and postpetiole with long erect hairs. Gastral tergite I with long decumbent and sparsely erect hairs.

Head, mesosoma, waist, gaster brown. Antennae and legs yellowish brown.

Etymology.

The species name eguchii is derived from the Japanese entomologist Dr. Katsuyuki Eguchi, who collected the type series.

Distribution.

Vietnam (Mt. Phansipan)

Remarks.

Three intermediates are recognized within the major worker subcaste of this species (Fig. 7 ). Ocelli are absent in intermediate 1; one median and one lateral ocellus are present in intermediate 2; and one median and two lateral ocelli are present in intermediate 3. Forward convexity of promesonotal suture in dorsal view becomes more pronounced from intermediate 1 to 3.

This species corresponds to Oligomyrmex sp. eg- 2 shown in Eguchi et al. (2011).

Figures

Figure 6. A – F. Carebara eguchii sp. nov. A – C. Holotype major worker (VNMN, collection code KUECCRB 011) from Vietnam; D – F. Paratype minor worker (KUEC, collection code KUECCRB 013) from Vietnam. A, D. Profile view of body; B, E. Head in full-face view; C, F. Dorsal view of body.

Figure 7. A – I. Intermediates of Carebara eguchii sp. nov. A – C. Intermediate 1 (Paratype, collection code KUECCRB 012); D – F. Intermediate 2 (Paratype, collection code KUEC 014); G – I. Intermediate 3 (Holotype, collection code KUECCRB 011). A, D, G. Head in full-face view; B, E, H. Profile view of body; C, F, I. Dorsal view of body.