Paratrechina

This genus contains the widely distributed pest species Paratrechina longicornis. LaPolla and Fisher (2014) - the center of Paratrechina diversity is in the Afrotropical and Malagasy regions, which raises some interesting questions as to the origin of the now pantropical P. longicornis (LaPolla et al. 2013). A review of the argument that P. longicornis is Asian in origin is provided by Wetterer (2008) and LaPolla et al. (2013) (i.e., on the observation that P. longicornis has only been found in undisturbed habitats in tropical Asia). However, since P. zanjensis appears to be a miombo woodland specialist and its sister taxon is almost certainly P. longicornis, it raises the possibility that P. longicornis might be an African woodland specialist as well. Given the fact that most African woodland habitat has been impacted to some extent by humans, it might be difficult to prove that P. longicornis is in fact native there. It is worth noting that the two new Malagasy species described here are native to dry forest habitats on limestone outcrops. While certainly P. kohli is a rainforest species, we cannot dismiss the possibility that it is the only species native to rainforests in the genus. There is one report of P. longicornis from native forest in Cameroon (Dejean et al. 1996). However, only one specimen of P. longicornis (out of 62,708 specimens) was collected from 15 forest sites in Tanzania (P. Hawkes, pers. comm.), so the conclusions of the previous study remain equivocal. Clearly, the question of the native range of P. longicornis remains an open one, but with the discovery of multiple Paratrechina species in the Afrotropical and Malagasy regions, a more complete survey is needed, and an Asian origin for the species now seems questionable.

Identification
Mandible with 5 teeth; maxillary palps 6-segmented; labial palps 4-segmented; erect setae on dorsum of head randomly placed; scapes lacking erect hairs; abundant erect setae on legs and dorsum of mesosoma. Eyes well developed and convex, surpassing outline of head in full frontal view, placed midlength and laterally on head. Dorsal mesosomal setae arranged loosely in pairs; propodeum lacking erect setae; propodeum with a low-domed dorsal face; overall mesosoma shape long and slender. (LaPolla et al. 2010)

Distribution
Paratrechina longicornis has been spread by humans and obtained a pantropical distribution. It is also found in temperate climates, largely through establishing itself in buildings and other artificial environments such as greenhouses. (Wetterer et al., 1999, Wetterer 2008). It is likely that this species arose in South-east Asia but this has yet to be confirmed (LaPolla et al., 2013; Wetterer, 2008).

Nomenclature

 *  PARATRECHINA [Formicinae: Plagiolepidini]
 * Paratrechina Motschoulsky, 1863: 13. Type-species: Paratrechina currens (junior synonym of Formica longicornis), by subsequent designation of Wheeler, W.M. 1911f: 170.
 * Paratrechina junior synonym of Prenolepis: Dalla Torre, 1893: 177; Wheeler, W.M. 1922a: 940.
 * Paratrechina revived from synonymy: Emery, 1925b: 216.

LaPolla and Fisher (2014) - Monomorphic, medium sized (2.1–3.2 mm in total length); ranging from almost black to brownish-yellow, with lighter mandibles, antennae (especially funicular segments towards tips) and legs (especially distal portion of tibiae and tarsi). Head with medially erect macrosetae roughly paired, extending through the medial portion of clypeus. Antennae 12 segmented; scapes long, with scape index above 140, in most species around or above 200 (SI range 143–226). Scapes with a dense layer of pubescence. Head is usually distinctly longer than wide, with cephalic index below 100 (CI range 71–94); posterolateral corners rounded, with straight posterior margin. Eyes large relative to head width (REL2 greater than 25); eyes distinctly convex, extending beyond head margin in full-face view. Mandibles in all species, except P. kohli, with 5 teeth; in P. kohli 8 teeth present, with 7th tooth on basal angle of mandible and 8th tooth on inner mandibular margin; mandalus large and anteriorly placed; palps very long; palp formula 6:4. Mesosoma elongated, most robust in P. kohli; most gracile in P. longicornis; propodeal dorsal face variable from either nearly flat (P. longicornis) or distinctly convex (P. antsingy); propodeum without macrosetae, anteriorly occasionally with a sparse layer of pubescence; pronotal setal count 6–12 (both sides of notum); mesonotal setal count 4–8 (both sides of notum). In lateral view, petiole cuneate, broadly rounded dorsally, with much longer posterior face and not surpassing the height of the propodeum. Legs distinctly long (profemur length 0.6–1.0 mm). Gaster robust, covered in abundant erect macrosetae.

Males are known only from Paratrechina longicornis (LaPolla et al. 2013), so it is impossible at this time to discuss general male characteristics for this genus.