Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Costa Rica and Panama. Costa Rica: lowland wet forest on both Atlantic and Pacific slopes.
Posterior third to half of dorsal surface of head smooth and shining, not finely striate; dorsal spine of petiole long and thin; head length less than 2.4mm; scape length less than head length (Brown 1976).
Odontomachus panamensis from Costa Rica and Panama, O. mayi from Amazonian Brazil, and O. affinis from wet forests of southeastern Brazil form a "tight subgroup" within the genus Odontomachus (Brown 1976). O. mayi is known to nest in ant gardens (discrete globular nests composed of accreted organic matter and dense masses of epiphytes, whose roots fill the interior of the nest), and often in a parabiotic association with Dolichoderus (formerly Monacis) rufescens (Mann 1912, Brown 1976). At the time of Brown's revision, nothing was known of the biology of O. panamensis.
At La Selva, O. panamensis is rarely encountered at ground-level, but is a common inhabitant of the canopy. It always inhabits ant gardens, and is usually in parabiotic association with a species in the Crematogaster limata parabiotica species complex. The feeding habits are unknown, but members of the genus Odontomachus are typically predators, using their elongate, violently-snapping mandibles to stun and transport prey.
The queens of O. panamensis are dimorphic. There is a "microgyne" form, which is smaller than workers, and a "macrogyne" form which is larger than workers. Both forms have been taken at blacklights, and both forms were collected from a single fogged tree of Virola koschnyi (ALAS collection number FVK/01), the crown of which was filled with numerous ant gardens.
I observed a pair of queens together under a small moss mat on an Inga tree, which suggests panamensis exhibits some form of claustral foundation of nests, and may be pleometrotic.
I made the following observations in June, 1997:
A film crew is at La Selva to film ant gardens. I climbed the Virola koschnyi at 300m on CES, a tree fogged by the ALAS project in 1993. There were ant gardens scattered in the crown. I climbed out on a branch to examine what I thought was a garden. It was where there had been a garden in 1993. Instead of a garden, I found that the branch was swollen. Parts of the stem had loose crumbly bark, and epiphyte roots were pushing through and under the bark. I wonder if antgardens can have a pathological effect on their host tree?
A member of the film crew climbed up to an active garden higher in the canopy. When he tapped it Odontomachus panamensis workers came out. He cut the branch with the garden and lowered it to the ground. We carried it back to the lab clearing, and the crew set it up for observation and filming in one of the shade houses. It was typical of many other antgardens I have seen at La Selva, with relatively small numbers of the larger O. panamensis occupying central chambers, and huge numbers of the tiny Crematogaster limata parabiotica nesting throughout the garden. The two species are constantly in close contact, but no overt signs of aggression occur. The two species appear to largely ignore each other.
I tentatively identified the epiphytes on the garden, using the photocopy herbarium at La Selva:
Columnea linearis (Gesneriaceae): a few dangling stems from garden, flowers, white globose fruits.
Clusia (Clusiaceae): possibly two species, one growing upright as small shrub on top, another with short pendant branch.
Bromeliaceae: there appeared to be three species.
Peperomia (Piperaceae): two species, one with larger leaves growing as a mat on top of garden, other creeping along branches away from garden.
Cactaceae: one strap-leaved plant on garden.
fern: linear-leaved species running on branches.
I found a fruiting aroid on a treefall branch. The small spadix had a number of globular white fruits. I brought it back and presented it to the Odontomachus. They showed great interest, snapped at the fruits, and when they were able to dislodge one they carried it back to the nest. The film crew broke some of the fruits open, and found seeds inside covered by an extremely sticky and viscous matrix. The ants would snap at the seeds and then struggle mightily to pull them free from the viscous pulp.
During the day, as the garden was being set up and filmed, the Odontomachus usually stayed inside. However, I went to inspect the garden at 2330hrs (near midnight) and dozens of Odontomachus workers were out on the garden surface and scattered over the branches. Thus it appears that O. panamensis forages nocturnally. When I checked again at 0600hrs, at first light, the workers had mostly returned. A few were still out on the surface of the nest.
The Crematogaster were abundant day and night, streaming in files from the nest out onto the branches and back.
Odontomachus affinis r. panamensis Forel 1899:19. Syntype worker, queen, male: Panama, Bugaba: Volcan de Chiriqui (Champion).
Brown, W. L., Jr. 1976. Contributions toward a reclassification of the Formicidae. Part VI. Ponerinae, tribe Ponerini, subtribe Odontomachiti. Section A. Introduction, subtribal characters. Genus Odontomachus. Studia Entomol. 19:67-171.
Forel, A. 1899. Formicidae. Biol. Cent.-Am. Hym. 3:1-160.
Mann, W. M. 1912. Parabiosis in Brazilian ants. Psyche 19:36-41.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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