Strumigenys clypeata group

AntWiki: The Ants --- Online

Strumigenys clypeata group Bolton (2000)

Species

Nearctic

Worker Diagnosis

Mandibles in full-face view and at full closure triangular, either serially dentate with masticatory margins that engage through all their exposed length or with a small edentate gap present between basal tooth and anterior clypeal margin. In ventral view outer margin of mandible without an inflected prebasal angle. MI 11-22.

Dentition. Principal tooth row with 5 sharp triangular teeth . Tooth 1 (basal) and 2 subequal in size, 3 distinctly longer (longest tooth on margin); tooth 4 reduced, smaller than 3 or 5. Tooth 5 followed by two small teeth , 4 minute denticles and a small apical tooth, giving a total dental count of 12.

Basal lamella of mandible triangular, usually longer than the longest tooth , not visible to mostly visible in full-face view with the mandibles fully closed. Either basal lamella not separated from basal tooth (adiastemate) or a small to moderate diastema present that is shorter to only slightly longer than length of basal tooth.

Labrum terminates in a pair of narrow digitate to conical lobes.

Clypeus with anterior margin convex in full-face view. Lateral clypea; margins approximately straight to feebly convex , and weakly to distinctly convergent anteriorly. Lateral clypeal margins not or slightly overlapping the outer margins of the fully closed mandibles. Clypeus with a peripheral groove that gives a bimarginate appearance (see discussion below).

Clypeal lateral margins with a fringe of anteriorly curved or anterolaterally inclined simple, spatulate or spoon-shaped hairs. Anterior margin with smaller hairs that may be directed anteriorly or weakly curved away from or toward the midline. Clypeal dorsum with appressed spatulate hairs or finer elevated pilosity.

Preocular carina broad and conspicuous in full-face view.

Ventrolateral margin of head between eye and mandible bluntly to quite sharply marginate.

Postbuccal impression small and shallow to vestigial.

Cuticle of side of head within scrobe reticulate or reticulate-punctate.

Scape moderate, SI 68-83, weakly to moderately dorsoventrally flattened, the dorsum and ventre converging anteriorly so that the leading edge is sharp or even a thin flange or lamella. Ventral surface of scape behind the leading edge may be weakly concave.

Leading edge of scape with simple to narrowly spatulate hairs, all of which are curved toward the apex of the scape.

Propodeum with triangular teeth subtended by a lamella on each side that is sometimes broad and engages the teeth through most of their length.

Spongiform appendages well developed on petiole and postpetiole; ventral spongiform curtain of petiole well developed. Base of first gastral sternite in profile with a narrow band or thin pad of weak or diffuse spongiform tissue.

Pilosity. Pronotal humeral hair long and flagellate. Dorsum of head behind clypeus with simple to narrowly spatulate ground-pilosity. Dorsolateral margin of head with apicoscrobal hair present or absent. Dorsal alitrunk , first gastral tergite and dorsal (outer) surface of hind basitarsus with flagellate hairs present.

Sculpture. Dorsum of head behind clypeus reticulate-punctate. Pleurae, side of propodeum and disc of postpetiole smooth.

Notes

In most (perhaps all) members of Pyramica the ventral surface of the clypeus has a small raised rim or carina that is set in from, but parallels, the free margin. In the clypeata-group this carina is hypertrophied and grows outward below the true margins so that it is clearly visible in frontal or profile view. It appears as a continuous second margin located below the true margin and projecting out nearly as far as, to even farther than, the original margin. Because of its origin as an outgrowth from below and behind the true clypeal margins the secondary (lower) margin is separated from the primary (upper) margin by an impression. Thus the edges of the clypeus appear bimarginate, with an upper margin and a lower margin, the two separated by a continuous peripheral groove.

Development of this feature is morphoclinal within the group. In clypeata and rohweri it is only weakly expressed (but obviously more strongly so in the latter than in the former) as the lower margin does not project out quite as far as the upper, and the vertical distance between the two is quite small. It can be seen in profile or frontal view but is best observed in specimens with open mandibles. In laevinasis and pilinasis the lower (secondary) margin is almost vertically beneath the upper, and about as strongly developed; the two are separated by a relatively broad concave groove. In bimarginata and filirrhina the lower margin extends out farther than the upper (primary) margin and becomes visible in dorsal view, but remains on a lower level, the two margins separated by a groove or gutter. Seen in full-face view these two species appear to have a concentrically double-rimmed or bimarginate clypeus.

Elsewhere in the genus there are species in which the lower (secondary) margin projects anteriorly, slightly beyond the true margin, immediately above the mandibles. In the Afrotropical region the lower margin is relatively well developed and prominent in all members of the very common lujae group, but tends to be difficult to see because it is overhung by hairs that arise from the primary margin.

The clypeata-group contains those species originally placed here by Brown (1953a) plus bimarginata and filirrhina. These last two were originally placed in their own group but have characters that definitely relate them closely with clypeata and its allies, or continue trends present in that group (see above).

References

Retrieved from "https://antwiki.org/wiki/index.php?title=Strumigenys_clypeata_group&oldid=557591"