Myagroteras

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Myagroteras
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Myrmoteratini
Genus: Myrmoteras
Subgenus: Myagroteras
Moffett, 1985
Type species
Myrmoteras donisthorpei

Myrmoteras donisthorpei casent0906286 p 1 high.jpg

Myrmoteras donisthorpei casent0906286 d 1 high.jpg

Specimen Labels

This is currently a subgenus of Myrmoteras. Please see below and the Myrmoteras webpage for additional information.

Subgeneric details

Moffett (1985) partitioned what was, at the time of his publication, the known species into subgenera and species groups. Many new species have been described since then, and the genus has more than doubled in the number of species. Authors describing new species after 1985 have mostly ignored assigning species to these subgenera and groups.

There is a key to all the species Moffett treated in his revisions of the genus: Key to Myrmoteras. The second subgenus, and details about it and its two species groups is found here: Myrmoteras species groups

Type. Myrmoteras donisthorpei by present selection. Name derived from Gr. myagra + teras, in reference to the trap-jaw prey capture technique.

Females lacking the long trigger hairs characteristic of the subgenus Myrmoteras species groups; instead labrum with a pair of short but conspicuous hairs (length less than 10% of mandible length). Dorsal surface of labrum (that is, the surface visible in dorsal full face view) not coming to a distinct anterior point; instead anterior margin rounded or truncate. The paired hairs originate well apart somewhat below the dorsal labral surface, and thus they are apparently positioned relatively lower on labrum than are trigger hairs in the subgenus Myrmoteras. The hairs are straight, and extend forward and strongly ventrad. Although more slender and differing somewhat in position, these hairs are possibly homologous with the trigger hairs found in the subgenus Myrmoteras.

In contrast to the subgenus Myrmoteras, frontal sulcus strongly developed, a conspicuous narrow to moderately wide groove (maximum width at least 0.01 mm) extending from the frontal area to the median ocellus (the single exception is Myrmoteras insulcatum, which completely lacks the sulcus). Both the orbital grooves and the ridges above antennal bases present, moderately developed to conspicuous. Frontal area demarcated to some degree. Except for the species M. insulcatum, clypeus higher and more strongly convex medially than in the subgenus Myrmoteras, and with lateral flanges better defined because of a more sudden shift in plane relative to the margins of the median region.

Mandibles relatively longer than in Myrmoteras, usually as long as or longer than trunk (ML/WL > 0.95 except in some M. morowali and indicum workers). Mandible shafts very feebly bent ventrad at position of penultimate tooth, angle of bend 20° or less; bend strongest in M. williamsi. When viewed from above outer margins of shafts feebly convex as in Myrmoteras, but often with a subtle inward bend at about a third of the distance from the mandible bases to the apical tooth (essentially lacking in Myrmoteras toro, Myrmoteras diastematum, and some Myrmoteras donisthorpei workers). Apical denticles relatively poorly developed, often smaller than in the subgenus Myrmoteras, with the largest invariably less than 18% of the length of the apical tooth.

Myagroteras species tend to be small, with none having head widths exceeding 1.10 mm. None of these ants has the feeble iridescence on the head and trunk characteristic of the Myrmoteras species in the binghami group.

This subgenus contains 11 species distributed from India to the Philippines. To date the greatest number of Myagroteras collections have been made in Borneo. The worker caste is known for ten species; the queen for nine; and males for four.

Two males have been collected from Hainan Island; one from Tien Fong Mountains is in the British Museum (Natural History) and the other (from Ta Han) is in the Museum of Comparative Zoology. Both are very similar to males of [[Myrmoteras bakeri and Myrmoteras donisthorpei and are therefore presumably in the subgenus Myagroteras (no males from the subgenus Myrmoteras have been described).

bakeri group

Mostly medium-sized (female size range 4.2 to 6.0 mm); smallest species Myrmoteras bakeri. Palpal segmentation varying from 5,3 to 4,2. Head and pronotum smooth, lacking sculpture, or with only traces of rugae. Rugae above antennal bases often conspicuous. Mandibles often with only a single apical denticle. Narrow ruga extends forward from base of each metathoracic tubercle as in the donisthorpei group (but absent in M. bakeri). Metanotal groove not visible as a conspicuously impressed notch in profile (but notch feebly developed in some M. bakeri). Ventral margin of petiole feebly convex beneath node.

Two species in this group are from Malaysia (including Sarawak and Sabah) and the third is from southern India.

donisthorpei group

Size small to medium. Palpal segmentation 5,4 or 5,3. Head and trunk sculptured as in williamsi group, but sculpture relatively delicate. A well-marked narrow ruga which clearly originates at the base of each metathoracic tubercle extends forward across mesothorax, effectively dividing mesothorax into dorsal and lateral areas. Metanotal groove not visible as a conspicuously impressed notch in profile. Petiole distinctive: sternum highly convex beneath node.

The group includes two species from Borneo, and apparently also Myrmoteras karnyi from the Mentawai Archipelago.

insulcatum group

Head and trunk highly polished, lacking sculpture. No trace of frontal sulcus on head (sulcus conspicuous in all other species in the subgenus). Clypeus only feebly convex medially, as in most species in the subgenus Myrmoteras. The two labral hairs presumed homologous with the trigger hairs of the subgenus Myrmoteras are more widely separated than in any other species of Myagroteras. Palpal segmentation 3,3. Mandibles with 14 to 15 teeth, the highest number recorded.

Known only from a single dealate queen from the Philippines.

williamsi group

Size small to medium (known range of females: TL 4.2 to 5.0 mm, except M. toro 5.2 to 5.6 mm). Head and pronotum strongly granulate or granulo-rugose. Orbital grooves moderately developed, less conspicuous than in other Myagroteras species. Postocular distance at least 20% of eye length (narrower in all other species in the genus). Palpal segmentation 6,4 (at least two workers in each species inspected where available). Lacking a conspicuous narrow ruga extending forward along sides of mesonotum from base of each metathoracic tubercle. Metanotal groove usually conspicuously impressed. Sternum of petiole feebly convex beneath node.

This group includes three closely related species from Sulawesi, all of which are new. These represent the first records of the genus Myrmoteras for Sulawesi, which now is the farthest the genus is known to extend to the southeast. In addition, I include here the distinctive Philippine species Myrmoteras williamsi.

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • MYAGROTERAS [subgenus of Myrmoteras]
    • Myagroteras Moffett, 1985b: 31 [as subgenus of Myrmoteras]. Type-species: Myrmoteras donisthorpei, by original designation.

References