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Costa Rica, Panama, Colombia (type locality), Trinidad, Brazil (GB, RJ, SP), Paraguay. Costa Rica: throughout country to about 1000m elevation.
This species inhabits wet to moist climate areas, in mature forest or second growth vegetation. In lowland sites it can occur in both mature and second growth forest, but at higher elevations is increasingly restricted to open or disturbed habitats. Workers are diurnal. The species is relatively common in canopy fogging samples at La Selva Biological Station.
Nests are in narrow-guage dead stems. Most nests I have encountered have been in stems 4-10mm outside diameter. Nests can be populous: a nest I found in a dead Cecropia petiole lodged in low vegetation contained 319 workers. Nests commonly occur in low vegetation, so the species is frequently encountered and collected.
Prior to this posting I mistakenly identified this species as trapezoideus Mayr. I examined Alex Wild's images of Mayr types and discovered that excisus and trapezoideus have a similar mesosoma shape, but excisus has bare cheeks and trapezoideus has hairy cheeks. The two species are sympatric in parts of South America, judging from some of my own collections from southern Guyana. Click here for Alex Wild type images.
Mayr, G. 1870. Formicidae novogranadenses. Sitzungsber. Kais. Akad. Wiss. Wien Math.-Naturwiss. Cl. Abt. I 61:370-417.
Alto Paraná, Canindeyú (ALWC, IFML, INBP, LACM). Literature records: Cordillera (Forel 1911b).
Found most commonly in these habitats: 64 times found in montane wet forest, 7 times found in Entre SHO y SSE, 9 times found in rainforest edge, 3 times found in CCL 400, 6 times found in SURA 850M, 5 times found in CCL 700m., 4 times found in Semideciduous seasonal forest, 6 times found in lowland rainforest, 4 times found in rainforest, 4 times found in 2º lowland rainforest, ...
Found most commonly in these microhabitats: 32 times Sobre Vegetacion, 13 times on low vegetation, 12 times beating veg., 10 times beating vegetation, 5 times ex sifted leaf litter, 4 times Sura, 1 times nest in dead stem Lantana, 4 times Copa de arbol, 2 times nest in dead stick, 3 times Malaise trap, 2 times in dead stick, ...
Collected most commonly using these methods: 68 times Fogging, 32 times Sweeping, 34 times Malaise, 22 times Beating, 7 times Foggin, 5 times miniWinkler, 2 times beating vegetation (3 hours), 3 times beating low vegetation, 2 times beating vegetation (1 hour), 2 times direct collection, 2 times malaise trap, ...
Elevations: collected from 5 - 1410 meters, 306 meters average