Tetraponera allaborans species group

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This article is based on Ward 2001, 2006.

Worker diagnosis

  • Small to medium-sized species (HW0.44 - 1.15)
  • Masticatory margin of mandible usually with four (rarely five) teeth, basal margin edentate and shorter than masticatory margin. In a subset of species (the T. allaborans complex) masticatory margin with three teeth, basal margin with 1 - 2 small teeth and longer than masticatory margin
  • Labrum without prominent teeth or tubercles or with a median tubercle near the proximal margin, widely flanked by a lateral pair
  • Anteromedial margin of clypeus variable (crenulate, toothed or entire)
  • Frontal carinal distance variable (FCI 0.08 - 0.22)
  • Scape length about two thirds of head width or less (SI 0.40 - 0.70)
  • Compound eyes directed anteriorly
  • Head capsule lacking ocelli, rarely with a weak lateral pair
  • Pronotum with weak to moderate lateral margination
  • Mesonotum about as long as wide, ovoid or subrectangular in dorsal view
  • Mesopropodeal impression usually containing a raised transverse metanotal (or mesoscutellar?) plate, but this reduced or lost in some species
  • Posteroventral margin of petiole well separated from the helcium venter
  • Metabasitarsal sulcus present
  • Mesosternum densely pubescent

This (above) is a more inclusive concept of the T. allaborans-group than that adopted in Ward (2001, see next paragraph). The posterior end of the petiole has a distinctive structure in the T. allaborans-group and in two other species groups of Tetraponera: the semicircular posterior margin of the sternite, against which the helcial sternite articulates, has retreated dorsomesially, and a new posteroventral margin protrudes below this. As a result the postpetiolar insertion has shifted upward, and the posteroventral margin of the petiole is well separated from it. The workers of the T. allaborans-group share this feature with the T. ambigua-group (from which they are distinguished by the orientation of the eyes and by differences in mesosomal structure) and with the T. natalensis-group (in which the workers lack the mesosternal pilosity seen in the T. allaborans-group and also have a differently shaped mesosoma).

The rest of this section is from Ward, 2001 and represent a less inclusive definition of the group than what is in use today (see above and Ward, 2009).

Workers of the allaborans-group can be recognised by the following features: (1) The mandible is slender, with the masticatory margin notably shorter than the basal margin and adorned with only three teeth. The basal margin has 1-2 small teeth or denticles. (2) With the head in full-face view, the dorsal abductor swelling at the base of the mandible is not visible, being hidden by the anterolateral extremity of the clypeus. (3) The mesopropodeal impression is well developed and open at the sides, the surface typically with irregular longitudinal rugulae that also extend down the side of the mesosoma. In one subset of species there is also a small, raised, transverse plate, an apparent metanotum. (4) The structure of the posterior end of the petiole has been substantially altered from the condition seen in other Asian species of Tetraponera: the semicircular margin of the petiolar sternite, against which the helcial sternites articulates, has retreated internally (dorsomesially) and a new, hood-like extension of the sternum has developed which forms the effective posterior margin. The result is that the lower part of the postpetiolar insertion is shifted dorsad, and there is a conspicuous space between the venter of the helcium and the posteroventral part of the petiole, when the postpetiole is in normal resting position (i.e. directed caudad). (5) Conspicuous standing pilosity is relatively sparse. There are usually only 1-2 pairs of long setae on the pronotum and none on the remainder of the mesosoma dorsum (exception: Tetraponera crassiuscula). (6) The mesosternum is densely pubescent almost throughout. (7) Abdominal tergite IV is sparsely pubescent.

Features (2) (4) (6) and (7) are also characteristic of the queen caste (known definitively for Tetraponera allaborans, Tetraponera bita, Tetraponera crassiuscula, Tetraponera extenuata and Tetraponera modesta). In addition, both males and queens of the allaborans-group have one cubital cell in the forewing. There are generally two cubital cells in other Asian/ Australian Tetraponera species for which the winged forms are known.

The males of the allaborans-group (known for T. allaborans, T. crassiuscula, T. extenuata and T. modesta) also share the following distinctive suite of characters, here contrasted with the corresponding condition in the nigra-group: (1) lateral arms of the hypopygiurn (sternite IX) extending outwards at right angles to the long axis of the sternite (nigra-group: arms protruding anteriorly and subtended by a thin lamellate plate); (2) paramere, inner proximal dorsal margin diverging gradually from midline (nigra-group: diverging at a sharply rounded angle from midline); (3) paramere, distal end, in posterolateral (or dorsal) view, with a very deep, obliquely transverse, dorsal impression (nigra-group: lacking such an impression); (4) aedeagus, lateral apodeme shorter than anterior apodeme (nigra-group: lateral apodeme as long as, or longer than, the anterior apodeme); (5) aedeagus, external face with a straight or slightly curved carina, originating anteromedially, directed distad, and meeting the posterior margin without forming a tooth or sharp angle (nigra-group: with an arched carina, directed posteroventrally, and terminating near a tooth or spine at the posteroventral extremity); (6) aedeagus, posterior margin bent laterad at a right angle to the sagittal plane (nigra-group: posterior margin directed posteriorly or posterolaterally).

Distribution

Africa, Madagascar, India to China, South to Northern Australia.

Valid Species

Related pages

References

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