Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Peru, Costa Rica. Costa Rica: Osa Peninsula.
Minor worker: eyes situated behind the scrobe, which terminates in front of the eye; lateral border of head convex and upturned above eye, without a rounded excision; petiole with distinct anterior and dorsal faces; lateral margins of mesosoma, including propodeal margins, denticulate, concolorous with rest of mesosoma; ventral surface of head largely punctate, at most weakly rugose; anterior face of petiole flat or convex, meeting dorsal face at obtuse angle; silvery hairs covering half or less of mesopleuron; lateral postpetiolar lobes short and blunt; ventral margin of postpetiole nearly flat, lacking anteroventral projection; compared to setulifer, postpetiole relatively narrow.
Major worker: unknown.
I know this species from one worker found in a recent treefall. The tree was a large canopy Inga in Corcovado National Park (Sirena).
Cephalotes peruviensis Andrade and Baroni Urbani 1999:555. Holotype (unique) worker: Peru, Madre de Dios, Avispas (Pena) [MCZC].
Andrade and Baroni Urbani recognized the coffeae clade that contained 4 extant and 7 fossil taxa. One of the distinct features of this clade is the presence of short erect setae on the gaster. Of the extant taxa, one is setulifer, an obligate plant-ant in Cordia alliodora, occurring commonly in Costa Rica and Panama (and one isolated record from Colombia). The other three are known from a few, geographically isolated records. coffeae is known from one nest collection from the live stem of a coffee plant in Colombia. peruviensis is known from a single worker from Avispa, Madre de Dios, Peru. trichophorus is known from two workers, one from Cuzco Amazonica, Madre de Dios, Peru, and one from Reserva Ducke, Amazonas, Brazil. These three differ in minor ways: details of the pronotal and propodeal dentition, and the degree of upturn of the frontal carinae over the eyes.
There appear to be two species of this clade in Costa Rica. In addition to abundant setulifer, I have one specimen that is closest to peruviensis. It differs from peruviensis in having three distinct denticles on the lateral pronotal margin, rather than two broad membraneous teeth, a notch, and three closely-spaced denticles. It has frontal carinae upturned over the eyes, a trait diagnostic for peruviensis. Andrade and Baroni Urbani did not hesitate to name new species from individual distinctive specimens, and would almost certainly have considered this specimen a new species. I prefer to call it peruviensis for now, pending greater knowledge of geographic variation in the clade.
I predict that C. peruviensis inhabits live stems and has a low foraging rate, which would explain its infrequent occurrence in collections. The occurrence of the coffeae types in a live stem and setulifer in live Cordia stems suggests that the whole clade may favor live stems. Manual collectors routinely break large numbers of dead stems looking for nests, but looking in live stems is more difficult and is not done as often. Dead stems are few in the environment, and represent a concentrated source of ant nests. In contrast, live stems are abundant, and finding cryptic ants in live stems is a "needle in the haystack" search.
The obligate plant-ant setulifer could easily have arisen through sympatric speciation with a source population of generalist live-stem nesting ants. One of the species in the clade that includes coffeae, peruviensis, and trichophorus could be the generalist progenitor of the more well-known setulifer.
Andrade, M. L. de, and C. Baroni Urbani. 1999. Diversity and adaptation in the ant genus Cephalotes, past and present (Hymenoptera, Formicidae). Stuttgarter Beitrage zur Naturkunde Serie B (Geologie und Palaontologie) 271:1-889.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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