Simopelta transversa

From an unpublished manuscript by Brown: the type colony was collected on a steep slope in the forest along a large stream. The ants were running rapidly downhill among moderately abundant leaf litter, all moving in the same direction. Almost all of them were carrying white pupae, and perhaps a few larvae, the brood of a medium-size Pheidole species. The column formed a bivouac consisting of a mass of workers, brood, and prey in a shallow basin of a leaf beneath another leaf. The colony size was estimated at 1000 or more adult workers. (as reported in Mackay and Mackay 2008)

Identification
Mackay and Mackay (2008) - Several species with transverse striae on the dorsum of the head could be confused with the workers of this species. It can be easily separated from all of them by the long, suberect hairs on the outer surface of the posterior tibia. Additionally, the node of the petiole (seen from above) is much broader than long, which is rare in the genus.

Key to Simopelta

Distribution based on Regional Taxon Lists
Neotropical Region: Colombia.

Nomenclature

 *  transversa. Simopelta transversa Mackay & Mackay, 2008: 321, figs. 11, 13, 56-59 (w.q.) COLOMBIA.

Worker
The workers are moderately large specimens (total length 4.5 mm), dark reddish-brown, with lighter brown appendages and gaster. Head length ranges from 0.97-1.02 mm, head width from 0.77-0.83 mm. The mandibles have 3 teeth, which are approximately equal in size. The anterior border of the clypeus is broadly rounded, and the eyes are small (maximum diameter 0.05 - 0.07 mm), located more than two diameters from the anterior margin of the head. The scape (0.88 - 0.94 mm) extends approximately the first three funicular segments past the posterior lateral corner. The mesosoma (Weber’s length 1.48-1.60 mm) is deeply impressed at the metanotal suture. The anterior and posterior faces of the petiole are nearly parallel, and the dorsal face is moderately defined, and horizontal. The spiracular horns are moderately well-developed, and the subpetiolar process is triangular, with a concave posterior face.

The dorsum of the head is covered with coarse, transverse rugae or striae, which pass anteriorly on the sides of the head, as well as the ventral surface of the head. The dorsum of the pronotum, mesonotum, and propodeum have transverse rugulae (especially on the pronotum) or poorly defined striae (especially on the propodeum). The rugulae on the side of pronotum form concentric curves, those on the mesopleuron and propodeum are obliquely vertical, or completely vertical. The dorsum of the gaster is mostly smooth and glossy.

Erect hairs are present on the mandibles, clypeus, the dorsal and ventral surfaces of the head, the scape, the dorsum of the mesosoma, the petiole, and the gaster, the hairs on the legs are long and erect to suberect.

Queen
The female is small (total length 6 mm, Weber’s length 1.44 mm), with an enlarged gaster. The mandibles of the female are sickle-shaped, without teeth. The clypeal apron and the anterior margin of clypeus are concave medially. The head is nearly round (head length 0.88 mm, head width 1.00 mm), and the eye is small (0.08 mm maximum diameter), located about three diameters from the anterior border of the head, and apparently contains about ten poorly defined ommatidia. The scapes are missing in the specimen (Brown, in an unpublished manuscript lists the length for this specimen as 0.65 mm). The dorsum of the pronotum is rounded, the scutum is rounded and convex, bulging, the scutellum is narrow and projecting strongly upwards, the propodeum is angulate posteriorly, the petiole is narrow when viewed in profile, composed of two distinct lobes when seen from the front. The subpetiolar process is strongly angulate, and directed ventrally.

The dorsum of the head of the female is covered with coarse punctures, and lacks the transverse rugae of the worker, the mesosoma is similar, and also lacks rugae. The dorsum of the gaster is moderately smooth and shining, but with roughened, granulate sculpture.

The dorsum of the head has several erect to decumbent hairs, as does the mesosoma, the hairs on the petiole are mostly erect, as are the hairs on the gaster, the hairs on the legs are mostly suberect.

Type Material
Holotype worker, 44 paratype workers (, , , , MCZC, , , ), 1 paratype female (MCZC), Pance, 1700m, Mun. of Cali, 16-vi, mt. rain forest; COLOMBIA: Valle, 1971.WL Brown S. Chaplin.

Etymology
From Latin, transversus meaning crosswise, referring to the rugae on the dorsum of the head. William Brown suggested the name.