Myrmoteras jaitrongi

Colonies are small, with less than 20 workers.

Identification
Bui, Eguchi and Yamane (2013) - Myrmoteras jaitrongi and Myrmoteras barbouri share the very small third tooth of mandible (called ‘the denticle between the penultimate tooth and the one proximad to it’ by Moffett, 1985). In this respect and the number of maxillary pulp segments (5), M. jaitrongi is closely related to M. barbouri, for which we could not examine the type material (Java). Our specimens may correspond to the smaller individuals of M. barbouri sensu Moffett (1985, p. 21) from the Malay Peninsula. However, M. jaitrongi differs from M. barbouri in the following respects: total body length including mandibles remarkably smaller (slightly more than 5 mm vs. 6.7–6.9 mm), dorsum of mesothorax rather regularly and transversely striate (irregularly or longitudinally rugose in M. barbouri), rugae on side of mesothorax more distinct in its posterior portion than in anterior portion (according to Creighton, 1930, five rugae present extending across the anterior half of the sides in M. barbouri), and generally much paler body colour (light brown vs. ferruginous; according to Creighton mesonotum and propodeum even tinged with black in M. barbouri).

Distribution
Southern Thailand and West Malaysia

Distribution based on Regional Taxon Lists
Indo-Australian Region: Malaysia. Oriental Region: Thailand.

Biology
Ito et al. (2017) were able to collect whole colonies. Nests were typically found under stones in the forest floor and were collected in Ulu Gombak (3°19’N; 101°45’E; 250 m a.s.l.), Selangor, Peninsular Malaysia between 1992 and 2016. Colonies are monogynous and queens found colonies non-claustrally. Colony size is very small, workers per colony = 9.2 + 4.4 (+ SD), N = 5, maximum 16. Ovariole number for queens is small with a total of just four per individual. Reproductive queens and larvae feed on liquid food from workers and solid prey items. M. jaitrongi make clusters of eggs and small larvae inside their nest. Workers of M. toro often held a larva or pupa by gently gripping them between the mandibles or immobilized them with their forelegs (Moffett 1986). Such behavior was rare in M. jaitrongi, as larvae and pupae were usually laid on the nest floor.

Foraging and contact with prey: Workers kept their mandibles fully opened (ca. 280 derees) most of the time they spent in the foraging arena. When they encountered prey animals, they slowly approached them. If prey animals moved fast, the workers chased the prey a bit but usually gave up. When they could be sufficiently close to have the prey within reach of the tips of the trigger hairs, they strike the prey by very quickly snapping the elongate mandibles. Closing the mandibles was powerful enough to kill the soft body arthropods they hunt for. When hunting for prey, workers never used formic acid, although they do possess a functional venom gland as is typical for formicine ants (Billen et al., 2015). When offered small (body length ca. 0.4 mm) and large springtails (ca. 1.3 mm) simultaneously, the ants preferred to attack the smaller prey. Beside springtails, they also attack young termite nymphs and small cricket nymphs. Foraging workers and virgin queens licked diluted sugar water in the foraging arena.

Prey feeding: Foraging ants brought prey items back to the nest chamber, and began to masti-cate prey by holding it between the tips of the mandibles. During prey mastication, workers and queens crossed the mandibles repeatedly, and sometimes adjusted the position of prey with their forelegs. They often fed on the masticated prey by bringing it with their forelegs to the mouthparts. After the foragers had fed on the prey they retrieved, they passed the masticated prey on to the larvae, fellow workers or both virgin and reproductive queens. When prey size was large, a few ants cooperatively masticated it. The queens and workers often fed on the masticated prey that was placed on the larval mouthparts. Inside the nest chamber, stomodeal trophallaxis among female individuals was often observed. Mated queens frequently received trophallaxis from workers, however, feeding directly on prey brought by workers was also observed. Oophagy was observed once. In this case, a worker picked up an egg from the nest floor, and destroyed it with the mandible tips. The queen nearby the worker immediately picked up the damaged egg, and fed on it.

Prey feeding: Foraging ants brought prey items back to the nest chamber, and began to masticate prey by holding it between the tips of the mandibles. During prey mastication, workers and queens crossed the mandibles repeatedly, and sometimes adjusted the position of prey with their forelegs. They often fed on the masticated prey by bringing it with their forelegs to the mouthparts. After the foragers had fed on the prey they retrieved, they passed the masticated prey on to the larvae, fellow workers or both virgin and reproductive queens. When prey size was large, a few ants cooperatively masticated it. The queens and workers often fed on the masticated prey that was placed on the larval mouthparts. Inside the nest chamber, stomodeal trophallaxis among female individuals was often observed. Mated queens frequently received trophallaxis from workers, however, feeding directly on prey brought by workers was also observed.

Brood care: Larvae and pupae were scattered on the nest floor. No clusters of eggs and microlarvae were organized. The reproductive queen rarely showed brood care, except for egg care just after oviposition.

Oviposition: Egg-laying by the queens was observed only once. The queen bent her abdomen forward underneath the thorax and extruded an egg from the tip of the abdomen. The egg was picked up by the queen herself with the mandibles. Worker egg-laying was observed once in M. jaitrongi. Egg-laying behavior was similar to queens, but as soon as the egg emerged from the abdominal tip, it was immediately eaten by the worker that had laid the egg.

Castes
Body size was similar for winged queens and workers, although queens had a slightly larger head (head width of M. jaitrongi queens, 1.07 + SD0.04mm,n=6; workers0.99+SD0.04mm, n=23), and a well-developed thorax. Queens have four ovarioles/individual (2+2) while workers have two ovarioles (1+1) (Ito et al. 2017).

Nomenclature

 *  jaitrongi. Myrmoteras jaitrongi Bui, Eguchi & Yamane, 2013: 551, figs. 1-B, 5 (w.) THAILAND.

Worker
TL 3.5, HL 0.98–1.02 (1.00), HW 0.88–0.94 (0.92), EL 0.62–0.67 (0.65), ML 1.35–1.42 (1.39), SL 1.12–1.23 (1.17), PrW 0.54–0.62 (0.58), HfL 1.17–1.31 (1.24), CI 90–92 (91), SI 126–131 (128). (Holotype and 2 non-type workers were measured.)

Body yellowish brown; gaster slightly darker than the mesosoma and petiole; legs yellowish. Body with sparse standing hairs, but without pubescence (clypeus with a few short appressed hairs). Clypeus weakly punctured or rugoso-punctate; frons mainly granulate, but area around antennal insertion finely rugoso-punctate; vertex of head (including occipital lobe) shining; frontal sulcus very feeble, visible as a very short trace running backward until the middle of frons. Anterior clypeal margin concave. Mandible with 9–10 teeth, and with two denticles between first and second teeth; third tooth much shorter than second and fourth teeth; palp formula 5,3. Orbital grooves virtually absent. Scape shorter than funicular segments combined. Funicular segments each longer than broad. Pronotum in lateral view with its dorsal outline gently sloping upward; dorsum of pronotum feebly punctured medially, almost smooth laterally; dorsum of mesonotum transversely and finely striate and its lateral face irregularly longitudinally or obliquely rugose; mesopleuron, metapleuron and propodeum smooth; metanotal groove shallow; propodeum in lateral view very weakly convex posterodorsally. Petiolar node round dorsally; ventral outline of petiole beneath the node slightly concave.

Type Material
Holotype worker from Thailand, Narathiwat Province, South-West Balahala: tropical rainforest, 7 xi 2002, leg. W. Jaitrong, WJT02-TH325 (THNHM-2002-3850). Paratype: 1 worker from the same locality as holotype, 25 ix 2001, leg. S. Hasin 2001.

Malaysia: 6 workers from Selangor, Ulu Gombak, vii–x 1992, leg. F. Ito, FI92MG; 1 worker, same locality, ca. 250 m alt., 5 vii 1999, leg. Sk. Yamane.
 * Non-type material examined.

Etymology
The specific name is dedicated to Dr. Weeyawat Jaitrong, who offered us valuable material.