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Pheidole arietansHNS new species

Types Mus. Comp. Zool. Harvard.

Etymology L arietansHNS, ramlike, referring to the forward-projecting frontal lobes of the major.

Diagnosis A distinctive member of the tristisHNS group characterized by the following traits.

Major: in side view, frontal lobe forms a conspicuous triangular projection; parallel transverse carinulae encircle the posterior half of the head; a wide band of rugoreticulum stretches from the posterior ends of each frontal lobe to the eye; the two frontal lobes are covered by a common set of parallel semicircular carinulae; promesonotum and propodeum covered by longitudinal carinulae. Minor: occiput broad, lacking a nuchal collar; margins of pronotal dorsum and all of mesonotal dorsum with transverse carinulae. Close to glyphodermaHNS, also of Costa Rica, but differing in many features of body form and sculpturing as illustrated. measurements (mm) Holotype major: HW 1.18, HL 1.34, SL 0.64, EL 0.16, PW 0.66. Paratype minor: HW 0.56, HL 0.60, SL 0.56, EL 0.12, PW 0.38.

color Major: posterior four-fifths of head capsule, and all of mesosomal dorsum, waist, and gaster dark brown; clypeus, a strip just posterior to the clypeus, mandibles, and side of mesosoma medium reddish brown; antennae and legs brownish yellow. Minor: body concolorous medium brown, appendages yellow to light brownish yellow.

Range Atlantic slope of Costa Rica from near sea level to 1000 m elevation (in Braulio Carrillo National Park) (Longino 1997).

Biology The type colony was collected by Stefan Cover in a hollow rotten stick on the floor of mature lowland rainforest. Seeds were present in the nest. Longino (1997) found one nest in a very wet rotten log, and others in internodes of Cecropia seedlings, as well as live stems of Myriocarpa along streams. One arboreal nest was found in a hollowed-out section ofa live branch in a fresh treefall; this colony had a seed cache.

figure Upper: holotype, major. Lower: paratype, minor. COSTA RICA: La Selva Biological Station, near Puerto Viejo, Heredia (Stefan Cover). Scale bars = 1 mm.