Pseudolasius

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Pseudolasius
Temporal range: 37.2–0 Ma Middle Eocene – Recent
Pseudolasius australis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Lasiini
Alliance: Prenolepis genus group
Genus: Pseudolasius
Emery, 1887
Type species
Formica familiaris, now Pseudolasius familiaris
Diversity
66 species
0 fossil species
(Species Checklist, Species by Country)

Pseudolasius australis casent0106005 profile 1.jpg

Pseudolasius australis

Pseudolasius australis casent0106005 dorsal 1.jpg

Specimen Label

Synonyms

Pseudolasius are perhaps best known for possessing a polymorphic worker caste, with most species having completely dimorphic majors (soldiers) and minors (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)

Keys including this Genus

 

Keys to Species in this Genus

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.

Distribution and Richness based on AntMaps

Species by Region

Number of species within biogeographic regions, along with the total number of species for each region.

Afrotropical Region Australasian Region Indo-Australian Region Malagasy Region Nearctic Region Neotropical Region Oriental Region Palaearctic Region
Species 0 1 47 0 0 0 13 9
Total Species 2840 1735 3042 932 835 4378 1740 2862

Fossils

Fossils are known from: Baltic amber (Bartonian, Middle to Late Eocene), Bitterfeld amber (Bartonian, Middle to Late Eocene) and Rovno amber (Priabonian, Late Eocene).

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. All three species carry their mealybugs (1) when disturbed, (2) during nest movements, and (3) to feeding sites. Ants build flat soil pavilions around their mealybug feeding sites and tend their trophobiosis partners. It is assumed that Pseudolasius queens do not co-disperse with their associated mealybugs during mating flight.

These Pseudolasius spp. are highly polydomous, which results in an extremely decentralized colony structure. Numerous small nest chambers were either widely distributed in the top soil (Pseudolasius sp.2 and sp.3) or predominantly in small decaying twigs (Pseudolasius sp.1). Pseudolasius sp. 1 and Pseudolasius sp. 2 are polygynous.

Association with Other Organisms

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Species Uncertain

  • An unknown species is a host for the phorid fly Pseudacteon sp. (a parasitoid) (Quevillon, 2018) (encounter mode primary; direct transmission; transmission outside nest).
  • An unknown species is a host for the phorid fly Pseudacteon sp. (a parasite) in Thailand (Brown & Fenner, 1998).

All Associate Records for Genus

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Taxon Relationship Associate Type Associate Taxon Associate Relationship Locality Source Notes
Pseudolasius host phorid fly Pseudacteon sp. parasite Thailand Brown & Fenner, 1998
Pseudolasius host phorid fly Pseudacteon sp. parasitoid Quevillon, 2018 encounter mode primary; direct transmission; transmission outside nest

Life History Traits

  • Mean colony size: 325 (Greer et al., 2021)
  • Compound colony type: not parasitic (Greer et al., 2021)
  • Nest site: hypogaeic (Greer et al., 2021)
  • Diet class: herbivore (Greer et al., 2021)
  • Foraging stratum: subterranean/leaf litter (Greer et al., 2021)

Castes

Head of worker Side of worker

Major worker of Pseudolasius from Queensland.

Head of worker Side of worker

Minor worker of Pseudolasius from Queensland.

Morphology

Worker Morphology

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• Antennal segment count: 11; 12 • Antennal club: absent-gradual, weak • Palp formula: 5,5; 5,3; 4,3 3,3; 2,3; 2,2 (5,3 in an undescribed species from Vietnam) • Total dental count: 4-7 • Spur formula: 1 simple, 1 simple; 0, 0 • Eyes: 11-100 ommatidia • Scrobes: absent • Pronotal Spines: absent • Mesonotal Spines: absent • Propodeal Spines: absent • Petiolar Spines: absent • Caste: mostly dimorphic or polymorphic • Sting: absent • Metaplural Gland: present • Cocoon: present

Karyotype

Species Uncertain

  • Pseudolasius sp.1: n = 8 (Malaysia) (Imai et al., 1983).
  • Pseudolasius sp.2: n = 15, 2n = 30 (Malaysia) (Imai et al., 1983) (B Chromosome polymorphism).
  • Pseudolasius sp.2: n = 17, 2n = 30 (Malaysia) (Imai et al., 1983) (B Chromosome polymorphism).
  • Pseudolasius sp.2: n = 19, 2n = 30 (Malaysia) (Imai et al., 1983) (B Chromosome polymorphism).
  • Pseudolasius: n = 14 (Taiwan) (Hung et al., 1972) (near Pseudolasius emeryi).
  • Pseudolasius: 2n = 30 (Indonesia) (Imai et al., 1985).
  • Pseudolasius: 2n = 30 (Sarawak) (Tjan et al., 1986).

All Karyotype Records for Genus

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Taxon Haploid Diploid Karyotype Locality Source Notes
Pseudolasius 30 Indonesia Imai et al., 1985
Pseudolasius 30 Sarawak Tjan et al., 1986
Pseudolasius 14 Taiwan Hung et al., 1972 near ''Pseudolasius emeryi''
Pseudolasius 15 30 Malaysia Imai et al., 1983 B Chromosome polymorphism
Pseudolasius 17 30 Malaysia Imai et al., 1983 B Chromosome polymorphism
Pseudolasius 19 30 Malaysia Imai et al., 1983 B Chromosome polymorphism
Pseudolasius 8 Malaysia Imai et al., 1983

Phylogeny

Formicinae
Myrmelachistini
Lasiini
Melophorini
Formicini
Gesomyrmecini

Gesomyrmex  (7 species, 12 fossil species)

Oecophyllini

Oecophylla  (15 species, 16 fossil species)

Plagiolepidini
Gigantiopini

Gigantiops  (1 species, 0 fossil species)

Santschiellini

Santschiella  (1 species, 0 fossil species)

Myrmoteratini

Myrmoteras  (41 species, 0 fossil species)

Camponotini

See Phylogeny of Formicinae for details.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • 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)

References