PARVIMYRMA

(Subfamily Myrmicinae)

Taxonomy

The genus Parvimyrma is recently established by Eguchi & Bui (2007) for a single species, P. sangi, found from N. Vietnam.

The worker of this tiny myrmicine ants has the following characteristics. Eguchi & Bui (2007) placed Parvimyrma in the Solenopsis genus group (sensu Bolton 1987, 2003) based on the combination of characteristics highlighted below in italic.

  • Body smooth to very weakly sculptured.
  • Frontal lobe in full-face view only partially concealing the toruli, not extending posteriorly as a frontal carina.
  • Antennal scrobe absent.
  • Posteromedian portion of clypeus narrowly inserted between frontal lobes.
  • Median clypeal seta well developed; 1st paracarinal seta well developed.
  • Lateral portions of clypeus not forming a raised rim or shield wall in front of the antennal insertions.
  • Mandible triangular, overlapping but not crossing over at full closure, with 5 distinct teeth on the masticatory margin but without any tooth/denticles on the basal margin; trulleum open.
  • Hypostoma with a conspicuous lateral tooth just mesal to each mandibular base; anterior margin of labrum broadly concave medially.
  • Palpal formula: maxillary 2 and labial 2.
  • Antenna 11-segmented, with a 2-segmented club; the apical antennal segment elongated much more than the preapical segment.
  • Eye completely absent.
  • Mesosoma in dorsal view constricted between promesonotum and propodeum.
  • Promesonotum low, in profile almost flat or very weakly convex dorsally, without conspicuous humerus.
  • Promesonotal suture completely absent dorsally.
  • Metanotal groove relatively shallowly impressed dorsally.
  • Meso and metatibial spur absent.
  • Propodeum unarmed but with a narrow cuticular rim on each posterolateral corner of the dorsum; the rim running downward and connecting with metapleural lobe.
  • Each meso and metasternum without a conspicuous process.
  • Metapleural lobes low and round.
  • Propodeal spiracle small, situated a little behind the midlength of the sides of propodeum.
  • Metapleural gland large.
  • Petiole pedunculate anteriorly and with a distinct node; the peduncle with a small anteroventral process.
  • Postpetiole much shorter than petiole, in dorsal view a little broader than petiolar node, narrowly attached to the anteriormost end of gaster.
  • Abdominal tergite IV (= gastral tergite I) broadly overlapping the sternite IV on the ventral surface of abdomen; gastral shoulder present.
  • Sting poorly developed.

Parvimyrma is easily distinguished from the other myrmicine genera known from the Indo-Chinese subregion by a combination of the following features: median clypeal seta well developed; posteromedian portion of clypeus narrowly inserted between frontal lobes; triangular mandible with 5 distinct teeth on the masticatory margin; antenna 11-segmented, with a 2-segmented club; eye completely absent. The 11-segmented antenna and the distinctly 5-teethed triangular mandible are only features by which Parvimyrma is distinguished from Solenopsis, the morphologically closest genus.

Images


Parvimyrma sangi, worker, body in lateral view.


Parvimyrma sangi, worker, head in full-face view.


Parvimyrma sangi, worker, mesosoma and waist in dorsal view.

Distribution

The only type series has so far been known for this monotypic genus.

sangi Eguchi et Bui W. Yen Tu NP (Bac Giang)

Bionomics

The type series of Parvimyrma sangi was obtained from one of ten cheese bait traps (small plastic tubes with several entrances containing powdered cheese as bait) buried ca. 10 cm underground in a well-developed forest at ca. 435 m alt. The circumstantial evidence as well as its morphological features (depigmentation and flat body without eyes) suggest that this species is a subterranean nester and forager (Eguchi & Bui 2007).

© Katsuyuki EGUCHI & BUI Tuan Viet, 2007. All rights reserved.