Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Range
Costa Rica, Panama, Guyana, Brazil (Para). Costa Rica: Atlantic and southern Pacific lowlands.
Identification
Minor worker: head length 0.39mm, head width 0.38mm, scape length 0.30mm, Webers length 0.38mm (n=1). Antenna 10-segmented; head somewhat flattened behind, with weak median indentation; mesonotal suture absent; propodeal spines moderately long; face and pronotum vary from shallowly foveolate to smooth and shiny; first gastral tergum smooth and shining; dorsal pilosity sparse, moderately long, stiff; color red brown.
Major worker: head length 0.72mm, head width 0.69mm, scape length 0.34mm (n=1). Face punctatorugose throughout; hypostomal margin gently curved, with median tooth, and a pair of stout teeth about one half distance from midline to recessed teeth flanking mandible bases (Figure); dorsal pilosity moderately abundant; head with abundant short setae projecting from sides of head in face view.
Natural History
This is a common canopy species that nests beneath epiphytes. Workers may also forage at or near ground level, and occasionally are found in open disturbed areas.
Selected Records
La Selva: the species has been taken most often in canopy fogging samples, as scattered foragers in recent treefalls, in nests beneath epiphytes in recent treefalls, and in the antgardens of Odontomachus panamensis. Workers have less commonly been taken in Malaise traps, and one collection is from a Winkler sample from the forest floor.
Sierpe: A small town in the southern Pacific lowlands, bordered by open agricultural land on one side, mangroves on the other; Longino found a worker in the small plaza in the town center; an open lawn with scattered ornamental trees.
Osa Peninsula: workers have been collected at extrafloral nectaries of Passiflora pittieri, near ground level.
Corcovado National Park (Sirena): in a a two day old treefall in primary forest. A nest was on and in a dead stick. There were two separate chambers in the stick, each one about 3mm wide and 10cm long, just under thin dead bark. The queen and most of the colony were not in these chambers, but rather outside under earth shelters. These earth shelters may have been old termite galleries. There were many minors, but only one major was seen.
Comments
The Pheidole perpusilla group contains species with 10-segmented antennae. The taxonomic status of the group as outlined by Wilson (2003) is as follows:
gemmula Wilson 2003. Amazonian Peru.
globularia Wilson 2003. Ecuador.
perpusilla Emery 1894. Panama to Amazonian Brazil.
= decem Forel 1901. Trinidad.
= emersoni Wheeler 1922. Guyana.
zeteki M. R. Smith 1947. Panama.
There is still plenty of confusion about what constitutes a species in this complex, and more work is needed. Species differences have been largely based on differences in sculpture on the face and pronotum. However, we have seen considerable variation in face sculpture among material from La Selva Biological Station, and we now consider this to be intraspecific variation within one population.
Pheidole perpusilla was described from Belem as being like flavens, with the same sculpture. This implies an entirely foveolate mesosoma and face. MCZ material that has 10-segmented antennae and completely foveolate face and mesosoma includes numerous collections from northern South America and collections from BCI, including the types of zeteki. Wilson kept perpusilla and zeteki as distinct species, with perpusilla having longitudinal rugulae that extend over the entire face of the major, and zeteki having longitudinal rugulae restricted to the anterior half. Wilson reported both species from BCI. We suspect the details of major face sculpture is intraspecifically variable and doubt there will be evidence for two sympatric species on BCI. Pheidole zeteki should be viewed as a potential synonym of perpusilla.
Wilson synonymized P. decem under perpusilla, and described the minor worker of perpusilla as having face and mesosoma completely foveolate and opaque. Yet the original description of decem describes the pronotum as smooth and shining. As noted above, such sculpture could be intraspecifically variable in perpusilla, and Wilson's synonymization of decem correct, but if so Wilson's diagnosis of perpusilla needs to be modified to include the variation.
At La Selva Biological Station what we are calling perpusilla has been frequently collected, and most specimens have a shallowly foveolate face and pronotum. The sculpture contrasts with the more strongly foveolate and opaque surface of perpusilla material from BCI. The few collections from the southern Pacific lowlands have a completely smooth and shiny face and pronotum, like the species gemmula and globularia from Ecuador and Peru. We used to consider these to be a different species, but further collecting at La Selva revealed variability in the degree of shininess on the face, and one collection approached the condition seen in Pacific slope material. So we are using the oldest name in the complex to refer to all the Costa Rica material until further research shows evidence of multiple species.
Literature Cited
Wilson, E. O. 2003. Pheidole in the New World: A Dominant, Hyperdiverse Ant Genus. Harvard University Press, Cambridge, Mass
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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