Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images: Queen, face view (small, large); lateral view (small, large); mandible (large). Worker from San Josˇ, face view (small, large); lateral view (small, large).
Range
Costa Rica (type locality). Widespread in country but not known from Osa Peninsula.
Identification
Size small; color black; scapes long; compound eye with at least 5 ommatidia; propodeal spiracle large; petiolar node thin and scale-like (not symmetrical and subtriangular like JTL-007); weakly polymorphic.
Natural History
This is one of the most abundant Solenopsis species in Costa Rica. It does not occur in cloud forest, but is common in mid to lower elevation wet and moist forest. I have collected it in many localities throughout the Atlantic slope (to about 1000m), in moist forest areas near Monteverde, in the "bosque humedo" of Santa Rosa National Park, at La Alturas in the Cordillera de Talamanca, and in San Josˇ city parks. It is rare or absent in the wet forests of the southern Pacific lowlands, although I did collect it in the town plaza of Sierpe.
Solenopsis picea is most abundant in second growth forest or other altered habitats where there are trees, but it also occurs with some frequency in mature forest. It is arboreal, nesting in dead sticks, under epiphytes, and opportunistically in any arboreal cavity. Colonies are enormous, polydomous, and abundantly polygynous. They are spread throughout the vegetation and it is difficult to delimit colony boundaries. I have found dead sticks packed with abundant queens, some alate and some dealate, suggesting adoption of daughter queens into the colony.
In several ways workers are intermediate between fire ants and the tiny diplorhoptrum of leaf litter and soil. They are somewhat polymorphic, with considerable variation in worker size, but no really large soldiers. They are intermediate in size, with the smallest workers difficult to distinguish from small black diplorhoptrum of the leaf litter. They have small compound eyes, composed of five or more ommatidia. Diplorhoptrum usually have fewer, and fire ants usually have more.
Workers are omnivorous foragers, harvesting dead arthropods and recruiting to baits. Workers extend their foraging onto the ground and into the leaf litter, because they often occur in Winkler samples of sifted litter.
At La Selva Biological Station, S. picea is very common in the lab clearing. Masses of these tiny black ants are perennially found on the blacklight sheet, recruiting to dead insects that accumulate there.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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