Pseudolasius

Pseudolasius are perhaps best known for possessing a polymorphic worker caste, with most species possessing complete dimorphism, characterized by major and minor workers (LaPolla, 2004).

Identification
Mandible with 4 to 7 teeth; maxillary palps 2-to 5-segmented; labial palps 2- to 4-segmented; mandalus small and inconspicuous. Setae on dorsum of head randomly placed; with erect setae on scapes, legs and dorsum of mesosoma, including propodeum; body often covered in dense pubescence. Eyes often poorly developed, typically placed below midlength. Workers strongly polymorphic, with a major caste present; posterior margin of head in majors typically emarginate. Propodeum with a low- to high-domed dorsal face; overall mesosoma shape compact. (LaPolla et al. 2010)

Distribution
This genus is restricted to southern Asia, from India to China, stretching southwards to northern Australia. It appears to be restricted to tropical localities.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Biology
All species are apparently hypogeic. They convergently resemble Acropyga and especially subterraneous Lasius in colour and morphological characters, but are, however, polymorphic. The sociobiology of Pseudolasius is virtually unknown. In Malaysian lowland rainforests, three Pseudolasius species are involved in mutualistic relationships with a total of eight scale insect species in six genera feeding at the roots of plants (Malsch et al. 2001). The ants feed on honeydew excreted by the mealybug partners, and these (both adults and immature instars) are kept in chambers with and without ant brood.

Castes


Major worker of Pseudolasius from Queensland.



Minor worker of Pseudolasius from Queensland.

Worker Morphology
Palp formula 5,3 in an undescribed species from Vietnam.

Nomenclature

 *  PSEUDOLASIUS [Formicinae: Plagiolepidini]
 * Pseudolasius Emery, 1887a: 244. Type-species: Formica familiaris, by subsequent designation of Bingham, 1903: 337.
 * Pseudolasius senior synonym of Nesolasius: Bolton, 1994: 50.
 * NESOLASIUS [junior synonym of Pseudolasius]
 * Nesolasius Wheeler, W.M. 1935b: 50 [as subgenus of Pseudolasius]. Type-species: Pseudolasius (Nesolasius) typhlops, by original designation.
 * Nesolasius junior synonym of Pseudolasius: Bolton, 1994: 50.

The polymorphic nature of this genus is well known, but overall this is a fairly heterogeneous group that is in need of taxonomic revision. There are clearly some lineages that have taken a hypogaeic evolutionary route and look quite different from the larger, presumably epigaeic species. (LaPolla et al. 2010)