Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Range
Costa Rica: Atlantic and southern Pacific lowlands.
Identification
Minor worker: head length 0.72mm, head width 0.61mm, scape length 0.94mm, Webers length 0.96mm (n=1). Head evenly rounded behind, without vertex collar; promesonotal and metanotal grooves impressed; posterior border of metanotal groove somewhat step-like; anepisternum impressed relative to katepisternum; propodeal spines short; face smooth and shiny; pronotum smooth and shiny; katepisternum foveolate, overlain with oblique rugae; anepisternum and mesonotal dorsum largely smooth and shiny, with a few oblique rugae; lower sides of propodeum foveolate; dorsum of propodeum faintly foveolate; gaster smooth and shiny; dorsal pilosity moderately abundant, moderately long, flexuous; color red brown.
Variation: La Selva specimens are as above. Pacific slope specimens are a less robust version, with smaller propodeal spines, weaker sculpture on mesosoma, less step-like posterior border of metanotal groove.
Major worker: head length 2.05mm, head width 2.03mm, scape length 1.09mm (n=1). Face densely reticulate rugose foveolate, except for smooth and shiny in narrow medial furrow; hypostomal margin with pair of teeth, about 3/4 distance from midline to large recessed teeth flanking mandibles; setae on face, mesosoma, and gaster abundant, short, erect, flexuous; abundant short setae projecting from vertex lobes but not from sides of head in face view.
Variation: La Selva specimens are as above. Pacific slope specimens have projecting setae extending down sides of head in full face view.
Images above are of La Selva specimens. Additional images of Corcovado specimens: worker face view (original, reduced), worker lateral view (original, reduced), major face view (original, reduced), major lateral view (original, reduced).
Natural History
This species occurs in lowland wet forest. Nests are often in the soil, often in clay banks. Workers recruit to baits on the forest floor and are occasionally collected in Winkler samples.
Longino excavated a nest in a clay bank at La Selva. It had an irregular tumulus of soil around a slit-shaped entrance. A tunnel opened out into a 3-5mm wide gallery extending into the bank. There was a small chamber near the surface and a larger chamber about 15cm deep (horizontal in bank); the nest was not fully excavated and it is unknown if the nest extended deeper. Among the workers were several peculiar intercastes. These look like developmental aberrations. Wilson's revision contains two species, pepo and sphaerica, with this kind of morphology, and it is possible they are similar aberrations.
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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