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.

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.