Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Range
longiscapus s.l. (see comment): Colombia (type locality), Panama, Costa Rica. Costa Rica: Atlantic slope wet forest to 500m.
Identification
Mandibles with 5 teeth; preocular carina extending posteriorly, not curving mesad toward frontal carina; antennal scrobe more or less well defined; disk of first gastral tergite smooth, lacking longitudinal carinae; mesosomal dorsum with blunt mesonotal tubercles; metanotal groove impressed.
Natural History
This species inhabits wet forest habitats. It forms very distinctive nests on clay banks or on the undersurfaces of logs. In this respect it is very similar to Panamanian C. longiscapus, whose nest was described by Schultz et al. 2002. I made these observations on a nest at the 500m site on the Volcan Barva transect:
Mature forest understory, on short trail segment heading down to 500m refuge. A large rotten trunk was at a 45¡ angle. The undersurface was dark, with a layer of moist humus. The nest was a shell of accreted humus with the garden beneath. The shell was about 10cm across and 3cm deep. About 3cm to the side of it was a circular "auricle" of accreted soil, about 4cm across with walls about 2cm high, like an arena. The nest itself was contiguous with what looked like the remains of a similar arena. The covered nest was perfectly camouflaged, and I would not have seen it at all if the arena had not drawn my attention. The arena appeared abandoned, with some small stalked fungal or slime mold fruiting bodies on one edge, but the form of the structure was very geometrically regular. I saw no activity outside the nest, nor nest entrance, but when I broke through a small part of the ceiling the white garden was very visible and about a dozen workers rushed out. I collected some workers and a pinch of the garden, making a 1cm hole, but left the rest undisturbed. When I returned 3 hours later the hole was completely closed and completely integrated. The smooth surface showed no trace of the breach or the patch job.
Since this initial observation I have seen many nests, nearly always suspended from the roof of a concave portion of a clay bank, with a thin flared ring of accreted soil extending downward. Images of nests are provided below.
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This is the nest of a founding queen (Costa Rica, Pe–as Blancas Valley, 3 March 2005, J. Longino, JTL5466). The incipient fungus garden was suspended from the roof of the chamber, on a platform made of one forewing. The other forewing was unused on the floor of the chamber. The platform wing and discarded wing are visible in the lower right image.
Fern‡ndez-Mart’n et al. (2004) described the nest establishment behavior of a variety of attines and placed these behaviors in a phylogenetic context. Founding queens often attempt to isolate the incipient fungus garden from contact with chamber walls, presumably as a hygienic measure. In several lineages of attines (examined species of Myrmicocrypta, Mycocepurus, and Apterostigma) the founding queens attach one or two of their forewings to the ceiling and suspend the fungus garden from the forewing. Cyphomyrmex longiscapus from Panama facultatively placed wings horizontally on soil pillars on the chamber floor. This contrasts with the behavior observed here, which is more like that described for Myrmicocrypta, Mycocepurus, and Apterostigma.
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Incipient colony on a clay bank (Costa Rica, Braulio Carrillo National Park, 13 Apr 2004, J. Longino).
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Typical fluted funnel nest in upper bank near overhang (Costa Rica, Pe–as Blancas Valley, 4 Mar 2004, J. Longino, JTL5300). The nest was hidden behind a clump of soil suspended from roots (first image). The nest chamber was about 7cm dia. I collected much of nest contents, scooping them into a vial. Later I counted 266 workers; I never found a queen. The garden substrate looked like macerated plant fibers, yellow or light brown, often shaped into pellets, all covered with diaphanous white mycelium. Also there were small dark pellets that looked like insect frass or even soil pellets; I couldn't tell.
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Nest on a clay bank (Costa Rica, Braulio Carrillo National Park, 13 Apr 2004, J. Longino).
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Nest on a clay bank (Costa Rica, Braulio Carrillo National Park, 13 Apr 2004, J. Longino).
Comments
For nearly a decade I knew this species from a single worker I found at La Selva. It was alone in a small chamber on top of a rotten log. I never collected the species using any other method, in spite of intensive sampling with Winkler sifting, Berlese samples, Malaise traps, blacklight traps, and canopy fogging. Ted Schultz and others told me that clay banks have their own distinctive fauna. I began to search clay banks at the 300m site and in a short time found a nest. This reveals how a species can be relatively common, yet appear nearly invisible to standard sampling techniques due to a specialized nesting behavior.
Costa Rican workers are larger than Panamanian workers, and they are probably a separate species (Schultz, pers. com.). It is not clear which form is true longiscapus, and definitive identification must await further investigation.
Literature Cited
Fernandez-Marin, H., J. K. Zimmerman, and W. T. Wcislo. 2004. Ecological traits and evolutionary sequence of nest establishment in fungus-growing ants (Hymenoptera, Formicidae, Attini). Biological Journal of the Linnean Society 81:39-48.
Schultz, T. R., S. A. Solomon, U. G. Mueller, P. Villesen, J. J. Boomsma, R. M. M. Adams, and B. Norden. 2002. Cryptic speciation in the fungus-growing ants Cyphomyrmex longiscapus Weber and Cyphomyrmex muelleri Schultz and Solomon, new species (Formicidae, Attini). Insectes Sociaux 49:331-343.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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