Pheidole bilimeki

P. bilimeki as formally described may actually be two or more species. This ant can be common in the low arboreal zone of forests and other areas marginal nesting site habitats. It is extraordinarily adaptable in its choice of nest sites, and in Costa Rica at least, one of the most abundant of ant species. (Wilson 2003)

Identification
From Wilson (2003): An abundant, widespread member of the flavens group easily distinguished by the following combination of traits. Major: slender body form; humerus very prominent and lobose (see especially in dorsal-oblique view); postpetiole spinose, from above, petiolar node thin and tapered in side view; postpetiolar node low in side view; anterior two-thirds of dorsum of head longitudinally carinulate, not rugoreticulate, and all but the occiput and central piece of the clypeus foveolate and opaque; entire mesosoma and waist foveolate and opaque; anterior half of central strip of first gastral tergite shagreened and opaque. Minor: slender body form; all of body except gastral venter and second to terminal gastral tergites foveolate and opaque; postpetiolar node in side view very depressed.

There exists a complicated tangle of variation in this form and it is distributed across a wide area. Accordingly, Wilson (2003) stated the following:

Longino (1997) has correctly observed that two forms of this species (or two closely related species) occur in Costa Rica: a rainforest understory form (“anastasii”), with yellow minor workers, the occipital borders of which are convex with a weak median impression, and with majors possessing a foveolate occiput; and, coexisting with it in many places, a disturbed-habitat form (“annectans”), with yellow to brown minors, the occipital corners of which are more nearly straight and lack a median impression, and with majors possessing a shining occiput, I have now had the opportunity to examine extensive series from over all the range of bilimeki, including the types of bilimeki and all the infraspecific described variants listed in the synonymy. Longino may be correct, that two sibling species exist under bilimeki, but the variation is complex and its meaning uncertain. Forest series do tend to have majors with mostly foveolate occiputs over all the range, and disturbed-habitat series majors with shiny occiputs, although in both ecotypes there is considerable variation in the width of the shiny strip at or near the extreme occipital border. Both forms exhibit color variation in the minor, tending toward light to dark brown in montane localities. And the variation in the minor occiput is overall subtle and apparently continuous, and poorly correlated with minor head shape or major occipital sculpturation.

I have taken the conservative course in this complicated matter of recognizing only the single species bilimeki, until more detailed collections and field studies are forthcoming. If the division noted by Longino proves to correspond to two distinct species, then the name bilimeki (= anastasii = insulana = ares = antoniensis = jamaicensis) applies to the disturbed-habitat species, and annectans (= johnsoni) applies to the forest species. I cannot determine the placement of cellarum and venezuelana from my notes, but the relevance to nomenclature is moot. Although venezuelana was described the same year as annectans (1905), annectans was published at the earlier date (30 June 1905 versus 31 August 1905, for venezuelana). All of the infraspecific variation deserves a careful study, with correlative ecological analysis.

Distribution
From Nayarit, Veracruz, and Oaxaca in southern and western Mexico, through all of Central America to montane Colombia and Venezuela, and also the greater Antilles (Cuba, Jamaica, Haiti, Dominican Republic) to the Bahamas. Occurs from near sea level variously to 450 m (as in Colombia), 1250 m (Costa Rica), 1450 m (Honduras), and 1100 m (Venezuela, Dominican Republic). Not known from the Lesser Antilles. P. floridana may represent a northern geographic variant of bilimeki, or an endemic species modified by intergradation with a bilimeki immigrant population (q.v.). (Wilson 2003)

This taxon was described from Mexico.

Biology
P. bilimeki, whether a single species as broadly conceived, or two or more sibling species (bilimeki, annectans) is a specialist on the low arboreal zone of forests and other habitats that offer similar marginal nest sites. As such it is extraordinarily adaptable in its choice of nest sites, and in Costa Rica at least, one of the most abundant of ant species. There, as John T. Longino (1997) has observed, “Nests may be found in almost any kind of cavity or sheltered space, and [the ants] may augment their nest space by building galleries and tunnels with earthen construction. Nests have been observed in cavities in live stems of Cephaelis (Rubiaceae) and Pausandra trianae (Euphorbiaceae), bracts of Ischnosiphon (Marantaceae), clasping petiole bases of Araceae, and the bulbous leaf bases of Tillandsia bulbosa. It is a common opportunist inhabitant of myrmecophytes such as saplings of Cecropia, portions of myrmecophytic Ocotea trees abandoned by Myrmelachista, and myrmecophytic Piper species. In every Costa Rican population of myrmecophytic melastomes. . . that have been observed (Corcorado, La Selva, Tortuguero), this species has been the most abundant inhabitant. . . The species also nests in dead sticks and branches on or above the forest floor, and under bark flaps on tree trunks. When nests are in myrmecophytic melastomes, carton galleries may occur on the outside, connecting pouches and extending down the stem to the ground.” In rainforest at the La Selva Biological Station, near Puerto Viejo, I found bilimeki to be the most common Pheidole—in fact virtually the only one—in the loose, dry leaf litter that collects in the leafbase baskets of small palms up to two meters or so from the ground.

According to Longino (1997), the colonies are apparently polygynous, and also occupy multiple nests. A colony from Monteverde, Costa Rica, that I maintained in the laboratory proved both prolific and extraordinarily restless, emigrating from one chamber of the nest to another, and even out of the nest into the foraging arena, when disturbed even slightly. Minor worker scouts rapidly recruited large numbers of majors and other minors to baits, which they collected or dragged into the nest with swift dispatch even for a Pheidole. Large dead insects were hoisted and carried cooperatively. P. bilimeki evidently has a wide breeding season. Winged reproductives have been found in March, August, and December in Costa Rica; August in Honduras and Veracruz; June in Venezuela, Honduras, and the Dominican Republic; and October in Haiti.

Description
From Wilson (2003): An abundant, widespread member of the flavens group easily distinguished by the following combination of traits. Major: slender body form; humerus very prominent and lobose (see especially in dorsal-oblique view); postpetiole spinose, from above, petiolar node thin and tapered in side view; postpetiolar node low in side view; anterior two-thirds of dorsum of head longitudinally carinulate, not rugoreticulate, and all but the occiput and central piece of the clypeus foveolate and opaque; entire mesosoma and waist foveolate and opaque; anterior half of central strip of first gastral tergite shagreened and opaque. Minor: slender body form; all of body except gastral venter and second to terminal gastral tergites foveolate and opaque; postpetiolar node in side view very depressed.

Body concolorous light brownish yellow; variation among series ranges from mostly yellow to medium brown. Similar variation in minors among series ranges from clear yellow to dark brown. Over most of the range (in both the forest and disturbed-habitat forms) color usually but not always varies with elevation.

Measurements (mm): Lectotype major: HW 0.90, HL 0.96, SL 0.44, EL 0.12, PW 0.46.



'''Figure. Upper: major. Lower: minor. Scale bars = 1 mm.'''

Type Locality Information
COSTA RICA: Costa del Tablazo, 1500 m (syntypes of synonymous P. ares Forel, compared with bilimeki lectotype). (Type locality: Mexico.) (Wilson 2003)

Etymology
Patronym.