Strumigenys hindenburgi group

Strumigenys hindenburgi group Bolton (2000)

Species

Neotropical-Nearctic

Worker Diagnosis

Apical fork of mandible with one or two intercalary denticles; when two the lower denticle is the larger, the upper denticle usually minute and sometimes difficult to see. Mandible with a preapical tooth located close to the apicodorsal tooth, proximal of which the mandible is unarmed or has a variably-sized denticle that may be minute, or missing from one mandible, but which when present is always distal of the inner midlength of the mandible. MI 57-64.

Leading edge of scape with numerous extremely fine short soft simple hairs; either all curved toward the apex of the scape or 2-3 curved toward its base. Scape slender, subcylindrical, with an even shallow subbasal curve; short to moderate, SI 65-87.

Ventrolateral margin of head not indented nor deeply concave in front of eye. Postbuccal groove obtuse and shallow.

Pronotal humerus sharply angular or tuberculate in dorsal view.

Propodeum with narrowly triangular teeth subtended by a lamella on the declivity; without a sharp tooth or spine at base of declivity although a small rounded lobe may be present.

Ventral surface of petiole with a spongiform crest or curtain that may be broken or incomplete. Lateral spongiform lobe of petiole, and lateral and ventral lobes of postpetiole, large and dense. Base of first gastral sternite with a thick spongiform pad.

Pilosity. Pronotal humeral hair long, fine and flagellate. Ground-pilosity of head and alitrunk of soft fine curved simple short hairs; longer pilosity also entirely soft. Dorsolateral margin of head with 1-2 freely projecting flagellate hairs. Cephalic dorsum with one pair of anteriorly curved sub flagellate to flagellate standing hairs, near the occipital margin. Mesonotum with a pair of erect flagellate hairs. Waist segments and first gastral tergite with numerous to abundant long fine flagellate hairs. Anterior surface of first coxa very densely clothed with soft fine pubescence.

Sculpture. Head and alitrunk predominantly and often entirely densely sharply reticulate-punctate; weak rugulae may be present on head and pronotum and strong longitudinal rugulae may occur on promesonotum. A smooth area may be present on mesopleuron, metapleuron or both. Node of petiole and disc of postpetiole densely sculptured. Gastral sculpture variable, but basi gastral costulae always conspicuous.

Notes

A small but fairly compact group containing two complexes of two species each. All are marked by an abundance of fine soft pilosity and absence of spatulate or other stiff hairs that are so prevalent in the Neotropical species. The very dense fine pubescence on the anterior surfaces of the front coxae is characteristic; in hindenburgi this area is also flattened and may be glandular.

The older species were originally grouped together by Brown (1961), who said that only a single intercalary tooth was present in hindenburgi. In fact there are two intercalary articles, a larger and more conspicuous lower denticle or small tooth, and a much smaller insignificant upper denticle. The latter appears to be variable in size and may eventually prove to be absent in some samples, but it is present in the type-material and all others that I have seen. This miscount led hindenburgi through the wrong lug in the first couplet of Brown's (1962b) Neotropical Strumigenys key, and has since caused some misidentifications.

hindenburgi-complex

Strumigenys cosmostela, Strumigenys hindenburgi

Two or more hairs present on leading edge of the scape that curve toward the base of the scape. Apex of mandible with two intercalary denticles between the fork teeth, the upper of which may be small and difficult to see.

In both species the preapical tooth is distinct but the proximal preapical denticle is variable in size. It may be distinct, or so small that it is nothing more than a minute prominence on the upper inner mandibular margin, or in cosmostela may even be absent from one or both mandibles.

lanuginosa-complex

Strumigenys lanuginosa, Strumigenys vilhenai

All hairs on leading edge of scape curved toward the apex of the scape. Apex of mandible with a single small intercalary tooth between the fork teeth. In both species the preapical tooth is distinct but the proximal preapical denticle is absent in lanuginosa, present but minute in vilhenai.

References

Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.
Brown, W. L., Jr. 1961. The neotropical species of the ant genus Strumigenys Fr. Smith: miscellaneous concluding studies. Psyche. 68:58-69.