Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Identification
Minor worker: head length 0.67mm, head width 0.63mm, scape length 0.62mm, Webers length 0.79mm (n=1). Head rounded behind; promesonotum evenly arched, mesonotal suture weakly impressed; humeri projecting as pronounced teeth, each bearing a seta much longer than other mesosomal setae; mesonotum with small dorsal projections; propodeal spines very long, projecting posteriorly; face, mesosoma, and gaster largely smooth and shining; katepisternum, anepisternum, and part of side of propodeum foveolate; dorsal pilosity abundant, long, flexuous; color red brown to dark brown.
Major worker: head length 1.58mm, head width 1.34mm, scape length 0.58mm (n=1). Face densely punctatorugose throughout; scapes flat; shallow but distinct antennal scrobe; hypostomal margin with rounded medial tooth, pair of larger blunt teeth about one third distance to recessed teeth flanking mandible bases; dorsal pilosity abundant; head with abundant, short, bristle-like setae projecting from sides of head in face view.
Range
Costa Rica (both slopes to 800m).
Natural History
This species occurs in mature moist to wet forest. It nests in the soil, with a main nest chamber about 10cm deep. When workers excavate soil from the nest, they often form a characteristic flat arena around the nest entrance, surrounded by a pallisade-like ring of soil. Their nests contain seed caches, and the majors have massive heads, which suggest granivory as a major component of the diet. They are not restricted to granivory, however, since workers readily recruit to baits of various kinds.
Selected Records
Winkler samples and/or baits from Guanacaste Conservation Area (Maritza), Carara, Corcovado, Penas Blancas Valley, La Selva.
Penas Blancas Valley: Primary forest, clearing edge. Night collecting. Nest in clay soil in center of trail; pronounced annulus of excavated soil around the entrance. Flat arena around entrance with steep-sided walls about 2cm out (figure in notes). This form of crater could be due to soil texture (a very sticky clay). As I collected workers near the entrance, a soldier blocked the entrance with its head. Its head was flush with the surface of the ground, and completely filled the opening, effectively plugging the entrance. I excavated further. The nest center was about 10cm deep. It contained brood, more soldiers, workers, and a single colony queen.
Penas Blancas Valley: Wet forest. Night collecting, 2000-2200hrs. Aggregation of workers near a pile of small flower corollas on trail.
Corcovado (San Pedrillo): A nest in the center of the trail had a small, round entrance hole, no mound. Baiting with crisco-honey mix, chopped earthworm, and freshly killed tabanid brought minors but no majors. I dug up the colony and collected a few majors. The majors look like they could be seed crackers, and there were chambers with a few seeds that could have been granaries. The bulk of the nest was 10cm deep.
La Selva: nest in trail, typical flanged crater, seed cache in nest.
Page authors:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
Stefan Cover, Museum of Comparative Zoology, Harvard University, Cambridge MA 02138 USA. scover@oeb.harvard.edu
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