Carebara parva Wimolsuthikul & Jaitrong, 2024

Wimolsuthikul, Chaipat, Yamane, Seiki, Samung, Yudthana & Jaitrong, Weeyawat, 2024, A revision of the Carebara pygmaea (Emery, 1887) species group (Hymenoptera: Formicidae) in Thailand, Zootaxa 5481 (1), pp. 79-100 : 90-93

Carebara parva Wimolsuthikul & Jaitrong , sp. nov.

( Figs. 8–9 )

Type materials: Holotype major worker ( THNHM-I-00014199 , THNHM), southern Thailand, Surat Thani Province, Wipawadee District, Takuktai Subdistrict , 9.246468ºN, 98.946136ºE, 69 m a.s.l., 29.XII.2001, W. Jaitrong leg., WJT291201-10 . Paratypes: 2 major workers ( THNHM-I-00014200 , SKYC and THNHM-I-00019027 , THNHM) and 5 minor workers ( THNHM-I-00019028 to THNHM-I-00019031 , THNHM; THNHM-I-00014201 , SKYC) , same data as holotype .

Non-type material examined. Southern Thailand: Nakhon Si Thammarat Province, Phipun, Tapi Watershed , 13.X.2011, Sk. Yamane leg., TH11-SKY-087 ( SKYC) .

Measurements (in mm). Holotype (major worker): TL 3.2, HL 0.83, HW 0.79, SL 0.46, ED 0.04, ML 0.73, MW 0.4, DPW 0.13, PL 0.3, PH 0.2, CI 96, SI 58, PI1 150, PI2 44. Major worker (paratypes, n = 2): TL 3.27–3.43, HL 0.83–0.86, HW 0.79–0.83, SL 0.50–0.53, ED 0.05, ML 0.73–0.76, MW 0.4–0.43, DPW 0.17, PL 0.3–0.33, PH 0.23, CI 96, SI 60–67, PI1 129–143, PI2 50–56. Minor worker (paratypes, n=5): TL 1.82–1.88, HL 0.43–0.46, HW 0.36–0.4, SL 0.33–0.36, ED 0.01–0.02, ML 0.46–0.5, MW 0.2–0.23, DPW 0.10, PL 0.23–0.26, PH 0.13–0.17, CI 79–92, SI 91–92, PI1 160–200, PI2 38–43.

Diagnosis. Major: head and gastral tergite I with dense erect hairs mixed with decumbent hairs; promesonotum with sparse short erect hairs; with head in full-face view, posterior one-third with transverse striation, while anterior two-thirds with longitudinal striation; eye small, with ca. 5–6 ommatidia; gastral tergite I somewhat smooth and shiny; propodeal spine almost as long as or slightly longer than diameter of propodeal spiracle. Minor: propodeal dorsum smooth and shiny; petiole and postpetiole without hairs; propodeal junction bluntly angulate; body yellowish brown; smallest species found in Thailand (HW 0.79–0.83 mm in major worker; 0.36–0.4 mm in minor worker).

Descriptions. Major worker ( Fig. 8 ). Head in full-face view almost as long as broad, broadened medially, lateral margin convex and posterior margin shallowly concave medially; cephalic median furrow well-developed, extending posteriad to posterior margin of head. Mandible short, subtriangular. Clypeus broad, with anterior margin sinuate and at middle weakly convex. Frontal lobe poorly developed, only partly covering antennal socket; frontal carina inconspicuous, reaching level of anterior margin of eye. Eye small, with 5–6 ommatidia, located at anterior ¼ of head length laterally. Antenna 11-segmented with 2-segmented club; scape thin, clavate (its width at apex smaller than length of antennal segments X–XI combined), and short, when laid backward reaching mid-length of head. Mesosoma smaller than each of head and gaster; with mesosoma in profile view pronotum convex; promesonotal suture indistinct, present as weak groove dorsally; mesonotum relatively short, weakly convex; metanotal groove distinct; propodeal dorsal outline almost straight. Mesopleuron in profile clearly demarcated from metapleuron by deep groove; propodeal spine, short and subtriangular, pointed posterodorsally. Petiole with long anterior peduncle; petiolar node in profile relatively short, clearly higher than long. Postpetiole in dorsal view slightly broader than long; in profile view its dorsal outline weakly convex. Gaster in profile larger than head; anterior margin of gastral tergite I in dorsal view almost straight.

In full-face view posterior one-third of head with irregular transverse striation, anterior two-thirds punctate with longitudinal striation; lateral and ventral faces of head somewhat shiny; mandible and clypeus smooth and shiny; antennal scape somewhat smooth and shiny. Pronotum smooth and shiny; mesopleuron in profile finely punctate; propodeum largely punctate; legs entirely smooth and shiny. Petiole laterally punctate; petiolar node smooth and shiny; postpetiole entirely finely punctate. Gastral tergite I superficially shagreened with smooth and shiny interspaces.

Dorsum of head entirely covered with sparse erect hairs mixed with very short decumbent hairs; mandible with sparse decumbent hairs; antennal scape with dense appressed hairs.; pronotum with dense short decumbent hairs; mesonotum and dorsum of propodeum without erect hairs; legs with numerous short decumbent hairs. Peduncle of petiole without hairs; petiolar node with 5–6 erect hairs; postpetiole with sparse erect hairs on its dorsum; gastral tergite I covered with sparse erect hairs mixed with dense short decumbent hairs.

Body reddish brown; head darker than mesosoma and gaster; antenna and legs yellowish brown.

Minor worker ( Fig. 9 ). Head in full-face view longer than broad, with lateral margin convex and posterior margin almost straight. Mandible short, subtriangular. Clypeus broad, with its anterior margin roundly convex. Frontal lobe poorly developed, only partly covering antennal socket; frontal carina inconspicuous, reaching level of anterior margin of eye. Eye small, present as a black dot, located at anterior ¼ of head length laterally. Antenna 11-segmented with 2-segmented club; scape thin, clavate (its width at apex almost same as length of antennal segment X), when laid backward extending beyond mid-length of head but not reaching posterolateral corner of head. Mesosoma in dorsal view narrower than head and gaster. Mesonotum in profile roundly convex, sloping gradually to metanotal groove; promesonotal suture absent from dorsal view; metanotal groove distinct; propodeum relatively short, its dorsal outline almost straight with convex posterior junction; mesopleuron in profile demarcated from metapleuron by deep groove; propodeal spine absent. Petiole with long anterior peduncle; petiolar node in profile almost as long as high. Postpetiole in profile view very low with weakly convex dorsal outline, slightly longer than high. Gaster larger than head.

Head (including clypeus and mandible), promesonotum, propodeal dorsum, petiole, postpetiole, and gaster entirely smooth and shiny; antennal scape somewhat smooth and shiny; mesopleuron punctate; lateral face of propodeum faintly punctate; legs entirely smooth and shiny.

Dorsum of head entirely covered with dense short decumbent hairs, and with a pair of erect hairs on frontal carinae; antennal scape with dense decumbent hairs; entire mesosoma without erect hairs; promesonotum with sparse short decumbent hairs; propodeum with few decumbent hairs present; legs with numerous short decumbent hairs; petiole with sparse short decumbent hairs; postpetiole with sparse short erect hairs; gastral tergite I covered with dense short decumbent hairs.

Body yellowish brown; antenna, legs, and tip of gaster yellowish.

Etymology. The species epithet “ parva ” is a Latin word meaning small. This refers to the smallest species within this group found in Thailand.

Habitat. The type series was collected from a rotting log at the forest edge in southern Thailand.

Distribution. Thailand (Surat Thani Province, Fig. 13 ).

Remarks. Carebara parva is closely related to Carebara bokorensis and C. panhai , sharing characteristics such as erect hairs on the head and gastral tergite I in the major worker. As the smallest species in the group found in Thailand, it can be separated from C. bokorensis by the following characteristics in the major worker: 1) gastral tergite I smooth and shiny (punctate in C. bokorensis ); 2) posterior one-third of head with irregular striation (punctate, without striation in C. bokorensis ); 3) erect hairs on head and first gastral tergite I sparse and short (dense and long erect hairs in C. bokorensis , see figs 3 and 8 for comparison); 4) promesonotum weakly convex (distinctly convex to form a dome in C. bokorensis , see figs 3 and 8 for comparison); 5) mesosomal dorsum without erect hairs (with dense erect hairs in C. bokorensis ). This species is also similar to C. panhai but can be separated from the latter by the following characteristics: 1) in major worker, posterior one-third of head with irregular striation (posterior one-third of head with striation in C. panhai , see figs. 6C and 8C for comparison); 2) in major worker, promesonotum weakly convex (distinctly convex to form a dome in C. panhai , see figs. 6A and 8A for comparison); 3) in minor worker, scape shorter, reaching posterolateral corner of head (slightly extending posterolateral corner of head in C. panhai ).

Figures

FIGURE 8. Carebara parva Wimolsuthikul & Jaitrong, sp. nov., holotype major worker (THNHM-I-14199).A, Body in profile view; B, head in full-face view; C, body in dorsal view.

FIGURE 9. Carebara parva Wimolsuthikul & Jaitrong, sp. nov., paratype minor worker (THNHM-I-14201).A, Body in profile view; B, head in full-face view; 6C, body in dorsal view.

FIGURE 13. Distribution of Carebara pygmea species group in Thailand.