Key to Paratrechina Species
This key to the species of Paratrechina is based on LaPolla & Fisher (2014).
Workers of Paratrechina are relatively easy to identify to species based on morphology. In addition to the color and sculpture differences listed in the key and descriptions, the two Malagasy species have shorter scapes than P. longicornis and P. zanjensis (SI less than 195) relative to their head widths. The widespread P. longicornis has the lowest profile of any Paratrechina with an almost flat pronotum, mesonotum, and propodeum. Scape macrosetae are variable within the genus with both P. longicornis and P. kohli lacking them altogether, but P. ankarana, P. antsingy and P. zanjensis have abundant scape macrosetae. The REL2 is higher in P. longicornis and P. zanjensis than in the other species, typically well into the upper thirties and low forties. For the other three species the REL2 is typically in the upper twenties and low thirties, reflecting an overall wider head relative to eye length.
Only P. longicornis and P. zanjensis workers come closest to resembling one another and these can be easily separated based on the present or absence of scape macrosetae. Workers of all species, except P. kohli, have three small, but distinct, ocelli present. The number of mandibular teeth on P. kohli is particularly interesting. The tooth on the inner mandibular margin is separated from the basal angle tooth by a short diastema. It would not be surprising to occasionally find a P. kohli worker with more than 8 teeth because the single queen specimen known in collections has a tooth that is divided with two sets of cusps, implying more teeth might occasionally be expressed in individuals. In all other Paratrechina workers only five mandibular teeth are present.
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- Mandibles with eight teeth; six teeth on masticatory margin, one tooth on basal angle, another tooth on inner mandibular margin; head cuticle densely rugorecticulate =>Paratrechina kohli
- Mandibles with five teeth; head cuticle smooth and shiny => 2
- Scapes without macrosetae; dorsum of propodeum almost flat to very shallowly domed =>Paratrechina longicornis
- Scapes with macrosetae; dorsum of propodeum rounded, dome-like => 3
- Macrosetae dark brown, occasionally with lighter tips; SI greater than 195; Afrotropical region =>Paratrechina zanjensis
- Macrosetae yellow to whitish; SI less than 195; Malagasy region => 4
- Dark brown, with cuticle giving a faint greenish-blue reflection; propodeum with fine striations across surface =>Paratrechina ankarana
- Brown with patches of lighter cuticle across body, giving species a mottled appearance; propodeum smooth and very shiny =>Paratrechina antsingy