Attini, Myrmicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Costa Rica (type locality), Panama. Costa Rica: Atlantic and southern Pacific lowlands.
Metanotum lacking longitudinal carinae; anterior margin of clypeus convex, with thin fringe of smooth cuticle; mesosoma length about 1.7mm; scapes very long, extending far beyond vertex margin (scape length/head width 1.6); neck strongly developed; lateral margins of frontal lobes in face view rounded to gently angular, not appearing strongly inflated (cf. robustum).
Similar species: Apterostigma robustum has strongly inflated frontal lobes and relatively shorter antennal scapes.
Figure 1. Typical nest of Apterostigma collare beneath understory palm leaf. Click here for additional images of nests.
Apterostigma collare occurs in lowland wet forest and is the most conspicuous and frequently encountered species of Apterostigma. Nests are suspended from low vegetation, most often on the undersides of leaves, under low branches, or on trunks (fig. 1). The nest is a small mass of substrate and fungus covered with a delicate white sack. The sack is itself composed of fungal hyphae, and workers move in and out of the sack through a single entrance hole. Nests are usually 2-3cm long and 1cm high. Individual nests usually contain fewer than a dozen workers, and may or may not contain a queen. Nests are restricted to permanently humid, strongly shaded forest understory, often near streams.
Of several whole colonies I have collected, the largest contained 25 adult workers, 4 dealate queens, 14 alate queens, 10 pupae, and 5 large larvae. The smallest contained just a single worker. On several occasions I have collected nests with workers only. I do not know if colonies can establish with just workers, or if queens may be out foraging when the nest is collected. I examined two whole nest samples from Corcovado National Park on the Pacific side of Costa Rica and both were polygynous. In contrast, seven whole colonies from Atlantic slope forests were all monogynous or lacked queens.
At Refugio Eladio in the Pe–as Blancas Valley I found a particularly large nest, 10x7cm, on the underside of a leaf. While collecting some workers I nearly destroyed it, removing most of the hyphal envelope. I returned 45 days later and the nest had been rebuilt and looked just like it did before.
The small nests of A. collare are often quite abundant, and multiple nests can often be found within 1m of each other. Singer and Espelie (1998) investigated nestmate recognition and nest material recognition by workers and found that each nest was probably an independent colony. Workers rejected non-nestmates and foreign nest material, regardless of how far apart the nests were.
Forsyth (1981) and Black (1987) published reports on the biology of Apterostigma inhabiting exposed white fungus nests. The taxonomic understanding was such that collare, robustum, and dentigerum were probably not distinguished.
The species is redescribed by Lattke (1997).
Black, R. W. 1987. The biology of leaf nesting ants in a tropical wet forest. Biotropica 19:319-325.
Emery, C. 1896. Studi sulle formiche della fauna neotropica. XVII-XXV. Bull. Soc. Entomol. Ital. 28:33-107.
Forsyth, A. 1981. Sex ratio and parental investment in an ant population. Evolution 35:1252-1253.
Lattke, J. E. 1997. Revisi—n del gˇnero Apterostigma Mayr (Hymenoptera: Formicidae). Arq. Zool. (S‹o Paulo) 34:121-221.
Singer, T. L., and K. E. Espelie. 1998. Nest and nestmate recognition by a fungus-growing ant, Apterostigma collare Emery (Hymenoptera: Formicidae). Ethology 104:929-939.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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