PROBOLOMYRMEX

(Subfamily Proceratiinae)

Taxonomy

Probolomyrmex is the only genus-rank taxon of the tribe Probolomyrmecini under the subfamily Proceratiinae (Bolton 2003). Worker of Vietnamese species has a combination of the following features (see Taylor 1965; Bolton 2003).

  • Body hairless but with extremely fine pubescence, micro-punctate, overlain by scattered foveolae.
  • Shelf-like frotoclypeal region overhanging the mandidbles.
  • Frontal carina fused and forming a vertical plate.
  • Antennal socket located on shelf-like frotoclypeal region, fully exposed.
  • Antenna 12-segmented.
  • Mandible small, elongate-triangular, with acute apical tooth followed by a series of small denticles; outer surface of mandible with several thick and short setae.
  • Eye completely absent. (1)
  • Promesonotal suture and metanotal groove absent.
  • Abdominal tergite IV not vaulted and sternite IV not reduced (different from the members of the tribe Proceratiini) .
1) Eye completely absent in the Oriental and Australian species.

The Oriental and Australian species can be classified into two species group based on the worker morphology (Eguchi et al, 2006). The longinodus group is characterized by the petiole which is clearly longer than high, and subpetiolar process which is low with poorly developed posteroventral portion. Three species, dammermani, longinodus and longiscapus, are known from Vietnam. The greavesi group is characterized by the petiole which is at most a little longer than high, and subpetiolar process which is developed and somewhat rectangular. One species, vieti, is known from Vietnam.

Images


Probolomyrmex dammermani, worker, body in lateral view.


Probolomyrmex dammermani, worker, head in full-face view.

Distribution

The genus is circumtropical/subtropical in distribution: four species are Neotropical, three Ethiopian, two Australian, and ten Oriental. The following four species has so far been collected from Vietnam.

dammermani Wheeler Pu Mat NP (Nghe An)
longinodus Terayama et Ogata Phu Quoc NP (Kien Giang)
longiscapus Xu et Zeng Cuc Phuong NP (Ninh Binh)
vieti Eguchi et al. S. Cat Tien NP (Dong Nai)

Bionomics

Probolomyrmex species are rare in Vietnam. Their colonies has been in rotten wood on the forest floor and top soil in relatively well-developed forests. Although biology of Vietnamese species is almost unknown, Ito (1998) noted the following bionomic characteristics of P. dammermani found from W. Java, Indonesia. The species is a specialized predators of polyxenid millipedes. Colony size is small (14 workers on average, with a range 8–21) with one dealate queen who was mated and laid eggs. Both workers and queens had only one ovariole per ovary; workers have no smermatheca. Pupae are necked. These features may be constant with other congeneric species. Due to their rareness, small colony size, small body size and fast locomotion it is very difficult to collect full-colony samples.

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