Strumigenys trixodens group

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Strumigenys trixodens group Bolton (2000)

Species

Malesian-Oriental-East Palaeartic

Worker Diagnosis

Apical fork of mandible of 3 long spiniform teeth in a vertical series; without intercalary denticles and without preapical dentition. MI 53-56.

Anterior clypeal margin extremely shallowly evenly concave, almost transverse.

Scape slightly dorsoventrally flattened, broadest in apical third of its length. SI 77-85.

Apical antennomere not constricted basally.

Ventrolateral margin of head with a broad but shallow preocular impression. With head in profile the ventral outline with a broad shallowly concave impression behind the level of the eye; margin between this and postbuccal groove shallowly convex.

Propodeal teeth free; margin of declivity with a thin carina.

Spongiform appendages of waist segments all present; lateral lobe of petiole in profile small and posterior.

Pilosity. Pronotal humeral hair remiform, not strongly differentiated from the other main pilosity of the dorsal alitrunk. Apicoscrobal hair absent. First gastral tergite with flagellate hairs but such hairs not present on head or alitrunk where the main pilosity is remiform or long-spatulate. Hind tibia and basitarsus with very long suberect projecting hairs.

Sculpture. Reticulate-punctate on head and alitrunk dorsally, with extensive smooth areas on side of the latter. Gaster un sculptured except for basigastral costulae.

Notes

Like the members of the chapmani group and akalles group Strumigenys trixodens has a tridentate apical fork on the mandible, but the third tooth appears to have been acquired by a different evolutionary process. In trixodens the three teeth form a more or less vertical series and the middle tooth of the fork appears to be a secondarily hypertrophied intercalary tooth, that has become long and spiniform, between the original apicodorsal and apicoventral fork teeth. In contrast the tridentate fork seen in the chapmani- and akalles-groups appears to have originated by the acquisition of a new apicodorsal tooth, developed from a preapical tooth that has shifted to the apex and increased markedly in size. The original bidentate fork, now somewhat reduced, subtends the new apicodorsal tooth in these two groups.

References

  • Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.