Strumigenys appretiata group

Strumigenys appretiata group Bolton (2000)

Species

Neotropical

Worker Diagnosis

Mandibles in full-face view and at full closure short, powerfully developed and bear trap-like, with a marked gap present between the inner mandibular margins proximal to the basal teeth. Dentition fully interlocking distal of the gap. In profile the masticatory margin strongly down-curved distal of the clypeus, mostly nearly vertical with respect to the long axis of the head. In ventral view outer margin of mandible with a sharply inflected prebasal angle. MI 13-20.

Dentition. With 4 massive recurved teeth following the basal lamella; distal to these with 1-2 smaller teeth or denticles and a slightly larger apical tooth, giving a total dental count of 6 or 7.

Basal lamella large, broadly roughly triangular or truncated apically. Anterior margin of basal lamella clearly visible when mandibles fully closed, the lamellae forming the mediobasally converging proximal portions of the inner mandibular margins.

Labrum terminates in a pair of short, very broadly convex flat and flap-like lobes, the lobes wide and strongly prominent.

Clypeus short and broad. Anterior clypeal margin shallowly to deeply concave across its width. Lateral margins of clypeus weakly convergent anteriorly, projecting laterally well beyond the outer margins of the mandibles; the latter intersect the anterior clypeal margin at or close to its anterolateral angles.

Clypeal pilosity restricted to sparse short strongly appressed dorsal hairs that may be difficult to see; without projecting hairs laterally or dorsally.

Preocular carina not visible in full-face view, concealed by the massively expanded dorsolateral margin.

Ventrolateral margin of head in front of eye sharply marginate, the margination shallowly concave. Postbuccal impression broad, deep and very conspicuous.

Cuticle within the antennal scrobe smooth and shining, not reticulate-punctate.

Scape very short, SI 36-50, rounded in section or very feebly dorsoventrally compressed, without an acute or flange-like leading edge.

Leading edge of scape without projecting hairs of any description.

Frontal carinae in full-face view massively expanded laterally, their outer edges curving strongly downwards over the scrobes, which they overhang and conceal. Frontal carinae semi-translucent and with one or two more translucent fenestrae (at least one directly above the antennal insertion).

Head in full-face view always short and broad, CI 86-97.

Propodeum bidentate to bispinose, the declivity with a narrow lamella on each side.

Spongiform appendages. Petiole with ventral spongiform tissue vestigial (a small tooth surmounted by a narrow lamella) to absent; never with a flange or curtain of spongiform material that extends most or all of the length of the segment. Ventral spongiform lobe of postpetiole small to absent; not visible in dorsal view as it is concealed by the lateral lobe. Base of first gastral sternite in profile with a spongiform pad.

Pilosity. Pronotal humeral hair usually present (absent only in Strumigenys deinomastax). Cephalic dorsum without standing hairs of any form; dorsolateral margins of head without laterally projecting hairs; apicoscrobal hair absent. Mesonotum with a single pair of standing simple hairs; similar hairs also present on waist segments and first gastral tergite. Dorsal (outer) surfaces of middle and hind tibiae with decumbent to appressed short hairs that are simple to narrowly spatulate; no standing hairs present.

Sculpture. Dorsum of head behind clypeus smooth or with superficial reticular patterning; without strong sculpture and never reticulate-punctate. Promesonotal dorsum lightly sculptured to smooth; sides of alitrunk smooth and shining.

Notes

The ten species of this compact and well defined group are superficially very similar, with the combination of characters listed above. A striking feature within the group is the morphoclinal reduction of the ventral spongiform lobe of the postpetiole. In five species (deinomastax , Strumigenys glenognatha, Strumigenys raptans, Strumigenys teratrix, Strumigenys wheeleriana) the lobe is relatively large, easily visible, decidedly spongiform, and proportional in size with the lateral postpetiolar lobe. In Strumigenys halosis and Strumigenys siagodens it is much reduced but still distinct, with a broad convex ventral margin but very small with respect to the lateral lobe. In two species (appretiata, hadrodens) the lobe has diminished to a tiny flap or tooth situated anteriorly on the postpetiolar sternite and in the final species (Strumigenys xenochelyna) it is entirely absent. What advantage may be gained by the reduction or loss of the lobe is not apparent.

References

Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.