Pheidole arachnion Wilson, 2003, new species

Pheidole arachnion new species

Types Mus. Comp. Zool. Harvard.

Etymology Gr arachnion, cobweb, alluding to the loose rugoreticulum on the head of the major.

Diagnosis A member of the tristis group characterized by the following combination of traits.

Major: dark reddish brown; sides of head covered by loose rugoreticulum (i.e. with large interspaces); humeri and postpetiolar nodes seen from above cornulate (horn-shaped); lacking any trace of antennal scrobes.

Minor: propodeal spine reduced to an obtuse angle; body entirely smooth and shiny except for several carinulae on anterior half of dorsal surface of head, one of which loops on each side of the head in a semicircle from the end of the frontal lobe to the anterior clypeal border; a thin nuchal collar present.

Very similar to iracunda, also of Costa Rica, but differing in details in the characters as listed and illustrated. Measurements (mm) Holotype major: HW 1.80, HL 1.98, SL 0.76, EL 0.18, PW 0.90. Paratype minor: HW 0.60, HL 0.62, SL 0.74, EL 0.10, PW 0.40.

Color Major: body and mandibles dark reddish brown, other appendages light reddish brown. Minor: body plain medium brown, appendages brownish yellow.

Range Known from the Atlantic lowlands of Costa Rica.

Biology A nest was found in rotting wood in forest at the La Selva Biological Station, near Puerto Viejo.

Figure Upper: holotype, major. Lower: paratype, minor. COSTA RICA: Rio Reventazon, 3-5 km east of Turrialba, Cartago (William L. Brown). Scale bars = 1 mm.