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Seven nests were observed in dead wood near ground level.
One nest was observed in a dead log, 10-20cm dia, suspended horizontally about 1m high. The log was largely solid but waterlogged throughout. The outer layers were wet and slimy with many worms. The Pheidole colony was in small chambers in a soft rotten area, about 1cm below the upper surface. The soft area was thoroughly excavated, and no more of the nest was found, so this collection probably contained most or all of the colony.
Nests may occur in live stems. Two nests were observed in internodes of Cecropia insignis saplings. In one case the colony was polydomous. Two nests were observed in live stems of Myriocarpa along streams. A nest was observed in a live branch (identity unknown) in a fresh treefall. The nest was in a discrete hollowed-out area; the stem was solid elsewhere. There were no Homoptera on the walls of the nest. There was a seed cache in the nest chamber.
Pheidole arietans, lowland Costa Rica: minor worker with face completely smooth and shining, nearly black; katepisternum mostly smooth and shining, with foveolation restricted to ventral and posterior margins. Major worker with clypeus flat, smooth, matte, with only a trace of medial horn; sculpture on face posterior to clypeus a short series of arcing rugae that meet medially, followed by transverse rugulae; setae on sides of head suberect; medial portion of side of pronotum, almost entire katepisternum, and lateral propodeum anterior to spiracle smooth, shining, highly polished. This form occurs in the Costa Rican lowlands, from La Selva Biological Station to 500m on the Barva Transect; in the Peñas Blancas Valley at both Poco Sol station and Refugio Eladio, at 800m; and on the lower slope of Volcan Arenal at 700m.
Highland Barva Transect form, Costa Rica: minor worker face completely foveolate; somewhat lighter brown; katepisternum more extensively foveolate, with small shiny patch anterodorsally or almost entirely foveolate. Major worker with clypeus as in arietans; sculpture on face posterior to clypeus like arietans, but anterior arcing rugae may be replaced by irregular mesh of rugae; setae on sides of head suberect, like arietans; side of pronotum with more extensive faint rugulae crossing medial area, katepisternum with larger patch of foveolation ventrally, lateral propodeum anterior to spiracle more foveolate compared to arietans. This form occurs in higher elevation forest, on the Barva transect, 600-1100m.
Peñas Blancas form, Costa Rica: minor worker face faintly and irregularly rugulose foveolate (intermediate between entirely shiny face of arietans and fully foveolate face of highland Barva form and P. glyphoderma); somewhat lighter brown; sculpture on side of mesosoma similar to upland Barva form. Major worker like upland Barva form, with sculpture on side of mesosoma somewhat intermediate between that form and arietans. This form is known only from Refugio Eladio in the Peñas Blancas valley, at 800m, where it appears to be sympatric with P. arietans.
Pheidole glyphoderma, highland Costa Rica: minor worker same as highland Barva form. Major worker with clypeus more concave, sublucid instead of matte, with scattered faint longitudinal rugulae; medial face posterior to clypeus with entirely longitudinal rugulae that fan outward onto posterior lobes; setae on sides of head lanose, fully appressed; lateral pronotum with faint linear rugulae, katepisternum mostly smooth and shining, lateral propodeum anterior to spiracle foveolate. This form is known only from Monteverde cloud forest, at 1500m. It is rare in Monteverde, known from only two separate collections in spite of abundant collecting there.
Pheidole triumbonata, southern Mexico: minor worker same as glyphoderma. Major worker with clypeus more concave, sublucid like glyphoderma, medial clypeal carina more developed, extending almost entire length of clypeus on most specimens (very short and nearly obsolete in one); sculpture on face posterior to clypeus like arietans on most specimens, but one specimen with entirely longitudinal rugulae like glyphoderma; setae on sides of head suberect; sculpture on side of mesosoma like glyphoderma. This form is known from the type locality in Veracruz and two mid-elevation (500-1000m) sites in northern Chiapas.
Pheidole walkeri, lowland Honduras: minor workers of the type series were not examined, but from the illustrations in Wilson (2003) they are like P. arietans. Major worker with clypeus sublucid, medial clypeal carina moderately developed on one specimen, nearly obsolete on another; medial face posterior to clypeus with entirely longitudinal rugulae that fan outward onto posterior lobes; setae on sides of head subdecumbent.
Wilson (2003) identified a Monteverde collection as a new species, glyphoderma. We interpret this collection as within the range of variation of arietans. It is heavily sculptured, but appears to be at the end of a continuum from heavily sculptured forms to smooth and shiny forms.
Wilson, E. O. 2003. Pheidole in the New World: A Dominant, Hyperdiverse Ant Genus. Harvard University Press, Cambridge, Mass
|Pheidole walkeri||Wilson, E. O., 2003, Pheidole in the New World. A dominant, hyperdiverse ant genus., Cambridge, MA: Harvard University Press: 777, (download)||777||20017|
|Pheidole walkeri||Longino, J. T., 2009, Additions to the taxonomy of New World Pheidole (Hymenoptera: Formicidae)., Zootaxa 2181, pp. 1-90: 86-88, (download)||86-88||22820|
Found most commonly in these habitats: 29 times found in montane wet forest, 24 times found in ridgetop cloud forest, 14 times found in mature wet forest, 23 times found in montane rainforest, 12 times found in mesophil forest, 5 times found in wet forest, 12 times found in lowland rainforest, 2 times found in tropical wet forest, 4 times found in cloud forest, 1 times found in CCL 550, ...
Found most commonly in these microhabitats: 81 times at bait, 33 times ex sifted leaf litter, 2 times nest in dead wood, 1 times nest in dead stick, 2 times Primary forest, 4 times beating vegetation, 2 times at cookie bait, 1 times NOTES FOR COLLECTIONS #3291-s TO #3315 WERE LOST. NOTES WERE RECONSTRUCTED FROM, 1 times New second growth veg. behind house; bananas, Piper, tall grass. Colony in dead, 1 times nest in rotten wood, 1 times foragers, ...
Collected most commonly using these methods: 84 times baiting, 24 times miniWinkler, 9 times search, 9 times maxiWinkler, 3 times Lure/Bait, 4 times beating, 3 times Winkler, 1 times Berlese, 1 times Unknown, 1 times YPT.
Elevations: collected from 50 - 1560 meters, 800 meters average