Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Identification
Minor worker: head length 0.56mm, head width 0.48mm, scape length 0.54mm, Webers length 0.64mm (n=1). Head rounded behind, with median notch or excavation; mesonotal suture weakly impressed; propodeal spines moderately long, spiniform; face and mesosoma uniformly foveolate; first gastral tergum mat, not shining; dorsal pilosity sparse (about 8 setae on promesonotum), short, stiff; color yellow.
Major worker: head length 1.08mm, head width 1.00mm, scape length 0.54mm (n=1). Face foveolate throughout, overlain with subparallel, longitudinal rugae on anterior half; clypeus rugose, excavate anteriorly; hypostomal margin gently curved; median tooth rounded, small to absent; pair of stout teeth about one third distance to recessed teeth flanking mandible bases (Figure); dorsal pilosity moderately abundant; head with abundant, short setae projecting from sides of head in face view.
Range
Costa Rica, Guatemala. Costa Rica: wet forest areas throughout the country to 1000m elevation (Corcovado, Penas Blancas, La Selva, Tortuguero, Hitoy Cerere).
Natural History
This is a very abundant species in the low arboreal stratum of primary wet forest understory throughout Costa Rica. Nests may be found in almost any kind of cavity or sheltered space, and they may augment their nest space by building galleries and tunnels with carton or earthen construction. Nests have been observed in cavities in live stems of Cephaelis (Rubiaceae) and Pausandra trianae (Euphorbiaceae), bracts of Ischnosiphon (Marantaceae), clasping petiole bases of Araceae, and the bulbous leaf bases of Tillandsia bulbosa. It is a common opportunistic inhabitant of myrmecophytes such as saplings of Cecropia, portions of myrmecophytic Ocotea trees abandoned by Myrmelachista, and myrmecophytic Piper species. In every Costa Rican population of myrmecophytic melastomes (those with petiolar or laminar pouches; Conostegia setosa, Clidemia sp., Tococa sp.) that has been observed (Corcovado, La Selva, Tortuguero), this species has been the most abundant inhabitant. This was the dominant ant in Leanne Tennant's study of Conostegia setosa at La Selva (Tennant 1994). The species also nests in dead sticks and branches on or above the forest floor, and under bark flaps on tree trunks. When nests are in myrmecophytic melastomes, carton galleries may occur on the outside, connecting pouches and extending down the stem to the ground. Colonies appear to be polydomous. Workers are generalist foragers, and may be taken at baits or in samples of sifted leaf litter.
Comments
Wilson (2003) treated anastasii as a junior synonym of P. bilimeki Mayr 1870. He defined bilimeki as a highly variable species occurring from Mexico to northern South America and throughout the Greater Antilles. The type locality of bilimeki is Mexico. Wilson synonymized a large number of taxa under bilimeki, including the Costa Rican forms anastasii Emery 1896, anastasii cellarum Forel 1908, and floridana ares Forel 1908.
In Costa Rica there appear to be two distinct species that differ in color, minor worker head shape, and habitat preference. In one species the minor worker is yellow and the head is rounded behind with a weak medial impression, the major worker is foveolate on the vertex lobes, and the habitat preference is for wet forest understory, where it nests in dead or live plant cavities. This form matches the description of Emery's anastasii. The type locality of anastasii is Jimenez, near present day Guapiles in the Atlantic lowlands. Other species described from this locality, where Anastasio Alfaro collected in the late 1800's, are primary rainforest species similar to what one finds at La Selva Biological Station.
In the other species the minor worker is variable in color, from yellow to brown but most often brown, the posterior border of the head is more flattened, the vertex lobes of the majors are always shiny to some extent, and the habitat preference is for disturbed and synanthropic habitats such as beach edges, roadsides, and around houses. It occurs as a building pest at La Selva Biological Station, with abundant anastasii in the surrounding forest. Until Wilson's revision we referred to this species as annectens. Brown (1981) discussed annectens in a paper delimiting the widespread species P. punctatissima. He stated "The other forms assigned to punctatissima as subspecies and varieties by Wheeler (annectens, insulana, jamaicensis, j. var. barbouri and j. var. praetermissa) do not belong to the same species as punctatissima, and will be dealt with later." He then differentiated these forms from punctatissima, and ended with "They [the subspecies and varieties] are attached temporarily as forms of P. annectens." Thus Brown's concept of annectens was of a widespread form that had brown workers like punctatissima and preferred coastlines and other open or highly disturbed habitats.
Wilson recognized the potential for sibling species in Costa Rica, but then made the confusing statement "If the division noted by Longino proves to correspond to two distinct specis, then the name bilimeki (= anastasii = insulana =ares =antoniensis = jamaicensis) applies to the disturbed-habitat species, and annectans [sic] (= johnsoni) applies to the forest species." This seems incorrect, and perhaps Wilson meant to write "bilimeki (= annectens = insulana =ares =antoniensis = jamaicensis) applies to the disturbed-habitat species, and anastasii (= johnsoni) applies to the forest species."
Assuming Wilson meant the latter, we now use the name anastasii for the mature forest form and bilimeki for the disturbed area form. However, given the confusion in the complex, a reevaluation of species boundaries and all the associated type material is clearly needed, including a firmer understanding of bilimeki itself.
Literature Cited
Brown, W. L. Jr. 1981. Preliminary contributions toward a revision of the ant genus Pheidole (Hymenoptera: Formicdae). Part I. J. Kansas Ent. Soc. 54:523-530.
Tennant, L. 1994. The ecology of Wasmannia auropunctata in primary tropical rainforest in Costa Rica and Panama. Pp. 80-90 in Williams, D.F. [Ed.]. Exotic ants: biology, impact, and control of introduced species. Westview Press, Oxford, England.
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
Date of this version: 2 September 2003.
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