Opamyrma

A monotypic genus known from only a few workers and colonies (Opamyrma hungvuong) collected in central Vietnam and southern China (Yamada et al., 2020).

Identification
Yamane et al. (2008) - Opamyrma is similar to Apomyrma with several shared characteristics: the outer face of the labrum bears peglike teeth; the frontal lobe is absent; the antennal socket is directed almost dorsad; the sternite of the petiole is reduced to a small posteroventral sclerite, bounded by the conspicuous tergo-sternal sutures; and the third abdominal segment above the helcium has a free anterior face.

The features which separate Opamyrma from Apomyrma (see Brown et al 1971; Bolton 1990, 2003 for characterization of Apomyrma) are: preoccipital carina complete, almost encircling the head slightly before its posterior margin; clypeus posteriorly margined with a distinct continuous carina; petiole without a distinct anterior peduncle; abdominal segment III longer than IV, V and VI; segment VII longest among the segments III–VII; anteriormost part of abdominal sternite III produced anteriad to the same level as the anteriormost part of tergite III; segment IV with differentiated presternite.

Distribution
Only known from central Vietnam.

Species by Region
Number of species within biogeographic regions, along with the total number of species for each region.

Castes
Known only from the worker caste.

Nomenclature

 *  OPAMYRMA [Leptanillinae]
 * Opamyrma Yamane, Bui & Eguchi, 2008: 56. Type-species: Opamyrma hungvuong, by original designation.
 * Transferred to Leptanillinae: Ward & Fisher, 2016: 690.

Worker description. Preoccipital carina complete, almost encircling the head slightly before its posterior margin (“poc” in Fig. 4). Venter of head with a distinct and complete median furrow, with each anterolateral corner forming a process (“alc” in Fig. 3). Clypeus posteriorly margined with a distinct continuous carina (“pcc” in Fig. 3); median part of clypeus rather clearly divided into posterior horizontal portion and anterior steep slope; the posterior portion broadly inserted between antennal sockets, extending anteriorly to the level of posterior margin of the sockets; lateral part of clypeus narrow from front to back. Mandibular base with closed trulleum (“trl” in Fig. 3). Labrum on its outer face with at least two rows of peg-like denticles, each with more than 10 denticles (“lpd” in Fig. 3). Eye absent. Frontal lobe absent. Antennal sockets completely exposed in full-face view, directing almost dorsad, located in a large, roundly excavated area whose anterior wall is steep just behind the posterior margin of clypeus; the area not clearly defined posteriorly. Antenna 12- segmented, gradually incrassate from segment II to XII.

Mesosoma elongate, with a single furrow (“msf” in Figs. 6 & 7) which is deep and flexible and separates pronotum from the remaining part of mesosoma. Metapleural gland bulla round, occupying posterior twofifths of ventrolateral part of the pleuron; metapleural trench running below the bulla. Junction of dorsal and posterior faces of propodeum round without any transverse carina; posterior face of propodeum laterally without spines/carinae. Propodeal spiracle situated relatively low on the side of propodeum, near the weak furrow separating metapleuron from lateral side of propodeum. Propodeal lobe present, low and round.

Mid- and hind tibiae each with a reduced barbulate anterior spur (“ats” in Fig. 8) and a well-developed pectinate posterior spur (“pts” in Fig. 8). Pretarsal claws simple, without teeth.

Waist consisting of a single segment (petiole); petiole elongate, narrowly attached to abdominal segment III (gastral segment I), virtually without anterior peduncle; tergo-sternal sutures of petiole present as longitudinal furrows on ventrolateral edges that meet medially at 1/3 length of petiole from the base (“tss” in Fig. 10); the sternite of petiole reduced to a small posteroventral sclerite, bounded by the conspicuous tergo-sternal sutures; petiolar spiracle located anteriorly on the lateral face of petiole at its mid-height.

Gaster very long, laterally compressed, especially in posterior portion, in profile highest at the posterior end of abdominal segment VI (“absg-VI” in Fig. 11). Segment III (“absg-III” in Fig. 11) seen from above longer than broad, narrowed basally, longer than segments IV, V and VI, having a free anterior face above the helcium; anteriormost part of abdominal sternite III (“abs-III” in Fig.11) produced anteriad to the same level as the anteriormost part of tergite III (“abt-III” in Fig. 11). Segment IV with differentiated presternite (“ps-IV” in Fig. 11). Spiracles on segments V–VII concealed by the preceding segments. Segment VII (“absg-VII” in Fig. 11) longest among the segments III–VII. Pygidium (“abt-VII” in Fig. 11) and hypopygium (“abs-VII” in Fig. 11) unarmed.

Etymology
The genus name Opamyrma is an anagram of Apomyrma for the first three letters.