Pheidole scrobifera Emery 1896

Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

worker face view

worker lateral view

major face view

major lateral view


Minor worker: head length 0.53mm, head width 0.52mm, scape length 0.41mm, Webers length 0.62mm (n=1). Head flattened behind, shallowly excavate medially; mesonotal suture absent; humeri produced as prominent triangular bosses; propodeal spines stout, long; face and mesosoma foveolate throughout; first gastral tergum smooth and shining; dorsal pilosity moderately abundant, long, flexuous; color orange.

Major worker: head length 1.02mm, head width 0.88mm, scape length 0.45mm (n=1). Head with pronounced, deep antennal scrobes; anterior portion of face mat with short, irregular, longitudinal rugae; posterior portion of face and vertex lobes reticulate rugose foveolate; hypostomal margin gently curved; medial tooth prominent, triangular; medial tooth flanked by pair of large, triangular teeth that abut the bases of the mandibles [These are the teeth that are typically recessed from the hypostomal margin in other species. In this species they are out on the margin. In other species a pair of teeth often occur on the hypostomal margin between the median tooth and the recessed teeth. In this species those lateral teeth are visible as small raised welts or bosses on the inner base of the enlarged, triangular teeth that flank the mandibles]; the undersurface of the head, the large triangular teeth, and the flattened ventral surfaces of the mandibles all lie in the same plane, sharply delimiting an elliptical entrance to the buccal chamber; dorsal pilosity abundant; head with abundant, very short, curved setae projecting from sides of head in face view.


Costa Rica (Atlantic slope to 900m). Type locality: Jimenez (nr Guapiles).

Natural History

Inhabits mature wet forest; nests in dead wood on forest floor; nocturnal foragers have been observed; nests appear relatively common, yet workers are rarely taken in Winkler samples.

Selected Records

Braulio Carrillo National Park, 300m: Winkler sample.

Braulio Carrillo National Park, 500m: Mature wet forest. I cracked a dead stick in the leaf litter, and there were two Pheidole colonies of different species [scrobifera and truncula], separated by a 1cm plug of sawdust. They became mixed and fighting ensued.

Braulio Carrillo National Park, 500m: Mature wet forest edge. Nest in rotten stump in pasture.

Penas Blancas Valley: Winkler sample; nocturnal foragers.

Penas Blancas Valley: Wet forest clearing. A moss plug filled a hollow knot in Psidium trunk near house. These were under it.

Penas Blancas Valley: Fallen tree over stream; populous nest under bark and extending down into small cavities in dead wood.

Volcan Arenal: in dead wood on ground; forested ravine below Arenal Observatory Lodge.

Rio Pacuare at 200m: wet forest; under loose bark on dead wood.

La Selva: nesting in rotten stick on forest floor.


Most collections of this species have abundant erect setae on the gaster (minors and majors). Two nest series we have seen completely lack erect setae on the gaster of both minors and majors. Other than the lack of setae, they are identical to the typical form. The depilated forms are from two different localities (La Selva Biological Station and the Penas Blancas Valley), both areas where the typical setose form is found.

Page authors:

John T. Longino, The Evergreen State College, Olympia WA 98505 USA.

Stefan Cover, Museum of Comparative Zoology, Harvard University, Cambridge MA 02138 USA.

Date of this version: 27 March 2008.
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