Strumigenys louisianae group

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Strumigenys louisianae group Bolton (2000)



Worker Diagnosis

Apical fork of mandible with two in tercalary denticles, often about the same size but sometimes one slightly larger than the other. Mandible with a preapical tooth located near the apicodorsal tooth; proximal of this either without other preapical dentition or with a minute denticle. MI 50 - 70.

Leading edge of scape with a number of spatulate or spoon-shaped hairs that are curved toward the base of the scape. Scape slightly dorsoventrally compressed, with subbasal bend weak to quite strongly defined. SI 63 - 85.

Ventrolateral margin of head not or shallowly concave in front of eye. Postbuccal groove varying from shallow and obtuse to deeply incised.

Propodeum with a pair of teeth subtended by a narrow lamella or carina on the declivity; without a sharp tooth or spine at base of declivity.

Ventral surface of petiole without spongiform tissue or at most with a small lobe posteriorly below the node; a fine non-spongiform cuticular carina may be present. Lateral spongiform lobe of petiole vestigial to absent, at most hardly more than a weak expansion at the apex of the posterior collar. Lateral lobe of postpetiole small to vestigial, ventral lobe of postpetiole usually larger and distinct. Base of first gastral sternite with a narrow to vestigial spongiform pad.

Pilosity. Pronotal humeral hair simple or flagellate. Ground-pilosity of head and alitrunk of conspicuous small broadly spatulate to spoon-shaped hairs that are closely applied to the surface or appressed. Standing pilosity: apicoscrobal hair present; cephalic dorsum with one or two short erect pairs; mesonotum with 1 - 2 erect pairs; first gastral tergite with numerous curved stout hairs that are flattened apically, remiform, or weakly clavate.

Sculpture. Head and alitrunk reticulate-punctate, sometimes with a clear area on mesopleuron, more rarely also on metapleuron; usually without trace of rugulae on head and pronotal dorsum. Disc of postpetiole usually sculptured, only rarely mostly smooth. Sculpture of first gastral tergite varying from mostly smooth to wholly sculptured.


The principal species of this group, Strumigenys louisianae, is extremely widely distributed, is one of the most commonly encountered New World species, and is extremely variable as regards colour, sculpture and size. Brown (1961) has discussed the variation and at the same time has amassed an extensive synonymy (Brown, 1953a, 1961). I have modified Brown's concept slightly by newly synonymising one species that he maintained as distinct (producta) and reviving another from his synonymy (Strumigenys infidelis). The variation remains impenetrable and I strongly suspect that more than one, and maybe several, genuine species are currently concealed in louisianae. The four species that I recognise here (Strumigenys dubitata, infidelis, louisianae, Strumigenys mixta) can all be defined by the form of their specialised pilosity and a few other characters that are known to be consistent and stable at species rank in the genus as a whole. An independent and extensive revision of the material currently retained as louisianae will be necessary to resolve the identities of any separate species it may contain.