Myrmoteras diastematum

Specimens have been collected from rainforest and mixed dipterocarp forest, including in leaf litter extractions in Brunei (Heterick & Kitching, 2022).

Identification
Moffett (1985) - The conspicuous sulcus between the clypeus and frons is unique to this species; this and the exceptionally wide frontal sulcus and orbital grooves serve to readily distinguish the species from closely related Myrmoteras bakeri.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia.

Nomenclature

 *  diastematum. Myrmoteras (Myagroteras) diastematum Moffett, 1985b: 36, figs. 26, 29 (w.q.) BORNEO.

Worker
Holotype: TL 5.4, HW 0.98, HL 1.03 (CI 95), ML 1.53 (MI 149), SL 1.19 (SI 122), EL 0.64, HFL 1.28 (TWI 18), WL 1.50 mm; two other workers HW 1.01 and 1.10 mm. Frontal sulcus, orbital grooves, and gap between clypeus and head capsule wide, forming conspicuous trenches bordered in black. Frontal area clearly defined. Palpal segmentation 5,4 (three inspected). Mandibles with 8 to 11 teeth and 3 to 4 preapical denticles. Either one or two apical denticles, the smallest, when present, being very minute, and the largest somewhat more massive than that of M. bakeri. Mandibular groove present, extending medially down shafts as described for Myrmoteras morowali.

Shape of trunk and petiole as in M. bakeri, but petiolar node not as high and posterior face less steep.

Head smooth except for rugae curving above antennal bases; pronotum smooth except for a few short longitudinal rugae on anterior face extending up from neck; mesothorax with several well separated narrow longitudinal rugae laterally, and feebly granulate dorsally, with indistinct fine longitudinal rugae. Propodeum dorsally with feeble narrow transverse rugae ca. 0.01 to 0.02 mm apart which fade out on sides at about level of spiracle; declivity virtually smooth. Pilosity very dense, with more than 40 hairs breaking dorsal margin of trunk when viewed in profile. Hairs long, rising 0.13 to 0.15 mm on head and 0.18 to 0.20 mm on trunk and gaster; 3 to 4 hairs on or near each metathoracic tubercle and 8 to 11 on node of petiole. Lighter in color than other diastematum material, including paratype queen described below, and thus probably somewhat teneral: head orange; legs darker orange; trunk and petiole yellowish orange; antennae and mandibles orange yellow; gaster brownish red.

Queen
Paratype with same collection number as holotype (HW 0.98) and two other Sarawak queens measured: TL 5.4 to 6.0, HW 0.98 to 1.06, HL 1.01 to 1.10 (CI 94 to 97), ML 1.43 to 1.56 (MI 141 to 142), SL 1.14 to 1.28 (SI 117 to 123), EL 0.63 to 0.68, HFL 1.23 to 1.35 (TWI 17 to 19), WL 1.50 to 1.68 mm. Mesonotum with conspicuous longitudinal rugae dorsally; remainder of trunk smooth except for feeble transverse rugae above neck on pronotum and very strongly developed transverse rugae 0.02 to 0.05 mm apart on dorsum of propodeum and extending obliquely across sides; declivitous face of propodeum smooth. Head orange red; clypeus, occipital lobe, legs and trunk reddish orange; petiole yellowish orange; antennae and mandibles orange yellow.

Type Material
Holotype. Worker deposited in from Borneo: Sarawak: 4th Division: Gunung Mulu National Park, v-viii.l978, B. M. 1978-49, camp 2 (P. M. Hammond and J. E. Marshall). Paratype. One dealate queen, same date and collection number as holotype (BMNH).

Etymology
Name derived from Gr. diastema, referring to the wide sulci on the head.

References based on Global Ant Biodiversity Informatics

 * Agosti D. 1992. Revision of the ant genus Myrmoteras of the Malay Archipelago (Hymenoptera, Formicidae). Rev. Suisse Zool. 99: 405-429.
 * Agosti, D. 1992. Revision of the ant genus Myrmoteras of the Malay Archipelago (Hymenoptera, Formicidae). Rev. Suisse Zool. 99: 405-429
 * CSIRO Collection
 * Moffett M.W. 1985. Revision of the genus Myrmoteras. Bulletin of the Museum of Comparative Zoology 151: 1-53.
 * Pfeiffer M., and D. Mezger. 2012. Biodiversity Assessment in Incomplete Inventories: Leaf Litter Ant Communities in Several Types of Bornean Rain Forest. PLoS ONE 7(7): e40729. doi:10.1371/journal.pone.0040869
 * Pfeiffer M., and D. Mezger. 2012. Biodiversity Assessment in Incomplete Inventories: Leaf Litter Ant Communities in Several Types of Bornean Rain Forest. PLoS ONE 7(7): e40729. doi:10.1371/journal.pone.0041054
 * Pfeiffer M.; Mezger, D.; Hosoishi, S.; Bakhtiar, E. Y.; Kohout, R. J. 2011. The Formicidae of Borneo (Insecta: Hymenoptera): a preliminary species list. Asian Myrmecology 4:9-58
 * Sukimin S., M. Mohamed, and H. Aris. 2010. Ant diversity of Maliau Basin Conservation Area, Sabah, Malaysia. Journal of Tropical Biology and Conservation 6:89-101.
 * Zettel H., and Sorger, D. M. 2011. New Myrmoteras ants (Hymenoptera: Formicidae) from the southeastern Philippines. Raffles Bulletin of Zoology 59:61-67.