Pheidole bicornis Forel 1899

Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

minor worker lateral view

major worker lateral view

minor worker face view

major worker face view

Atlantic lowlands

major worker face view

Pacific lowlands

Identification

Minor worker (La Selva): head length 0.54mm, head width 0.47mm, scape length 0.39mm, Webers length 0.67mm (n=1). Head somewhat flattened behind; promesonotum evenly arched, mesonotal suture absent; propodeal spines small but distinct; face smooth and shining, pronotum feebly punctatorugose dorsally, with large smooth and shiny patches on sides, mesonotum and propodeum foveolate; dorsal pilosity abundant, short, suberect, flexuous; color orange.

Major worker (La Selva): head length 1.04mm, head width 0.78mm, scape length 0.42mm (n=1). Anterior margins of frontal carinae in the form of distinct teeth, elevated and projecting from face; face entirely and coarsely punctatorugose, vermiculate rugae obliquely oriented in middle, irregular on sides, and transverse on vertex lobes; hypostomal margin nearly flat, with pair of sharp teeth located about one third distance from midline to recessed teeth flanking mandibles; dorsal pilosity abundant, short, somewhat lanose; sides of head with appressed to subdecumbent short pilosity, without conspicuous erect setae.

Variation: major workers from the Pacific side of Costa Rica have relatively wider heads (head length 1.06mm, head width 0.91mm, n=1), the hypostomal margin more concave, and the hypostomal teeth much smaller (n = 4 Pacific slope collections, 3 Atlantic slope collections).

Range

Panama (type locality Bugaba), Costa Rica (Atlantic and southern Pacific lowlands).

Natural History

This species is an obligate inhabitant of Piper myrmecophytes. Nests are in the clasping petioles, and may extend into the stem. Longino observed a colony in Corcovado National Park with 45 major workers, 70 minor workers, 7 adult males, 1 dealate queen, and brood. Most colonies observed by Longino have been monogynous, but one at Carara (Bijagual) was polygynous.

This species has been the subject of extensive ecological studies by Letourneau:

Letourneau, D. K. 1983. Passive aggression: an alternative hypothesis for the Piper-Pheidole association. Oecologia 60:122-126.

Letourneau, D. K. 1990. Code of ant-plant mutualism broken by parasite. Science 248:215-217.

Letourneau, D. K. 1991. Parasitism of ant-plant mutualisms and the novel case of Piper. Pp. 390-396 in C. Huxley and D. Cutler, eds. Ant-Plant Interactions. Oxford University Press, Oxford.


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: 3 December 1997


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