Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Range
Costa Rica (Atlantic lowland rainforest, to 600m elevation).
Identification
Opening of propodeal spiracle viewed perpendicularly slit-shaped, more than twice as long as wide (spiracle is very small, and boss around spiracle is round, but actual orifice still slit-shaped); petiole scale-shaped, tapering dorsally to rounded summit; mandible with 7 teeth, basal and masticatory margins distinct; lateral wings of clypeus divided by distinct transverse ridge, anterior portion distinctly concave and bent ventrad; frontal carinae closely approximated where they accomodate scapes, ratio of greatest distance between frontal carinae (across frontal lobes) to smallest distance 5.5; in lateral profile, anteroventral petiolar lobe short and deep, posterior margin subangular to square-cut.
Similar species: cauta, gilloglyi, stigma.
Natural History
This species occurs in mature lowland rainforest. I have numerous collections of workers and queens from under loose bark of dead wood on or near the ground. I occasionally collect workers from under dead wood, and I once collected workers from a dead branch from a recently fallen tree at La Selva (suggesting it can occur high in the canopy). It is odd that I have never collected this species in sifted leaf litter samples (Winkler samples). This suggests that even though it nests in rotten wood at ground level, it does not forage in the leaf litter.
Type Data
Ponera cognata Emery 1896:56. Syntype worker, queen: Costa Rica, Jimenez (Alfaro) [MCSN] (examined, 1990) [USNM] (examined, 1999).
Notes
I examined the type of cognata in Italy before I understood the difference between cognata and gilloglyi, two species that differ mainly in the form of the frontal carinae. I had been using the name cognata for the species with well separated frontal carinae. I recently examined a "cotype" of cognata at USNM, and it is the species with the closely approximated frontal carinae. The specimen bears a single handwritten label: "Trachymesopus cognatus Emery, Costa Rica, Cotype." I believe the handwriting is Emery's, and I assume the specimen is part of the original syntype series.
At USNM I found many stigma-complex nest series collected by F. Nevermann at Hamburg Farm, an Atlantic lowland site north of Limon. They had all been placed under stigma. I was able to separate them fairly easily into the species stigma, cognata, and gilloglyi, with stigma and cognata being the most common. This matches my experience at La Selva Biological Station and other sites in the Atlantic lowlands, where stigma and cognata are readily encountered by hand-collecting in dead wood at ground level, and gilloglyi is encountered under epiphytes in the canopy (or in recent treefalls). Pachycondyla succedanea is rarely encountered during hand collecting, and is more often obtained in Winkler samples of sifted leaf litter. Thus it is understandable that Nevermann, an excellent hand collector, did not encounter succedanea.
Literature Cited
Emery, C. 1896. Studi sulle formiche della fauna neotropica. XVII-XXV. Bullettino della Societa Entomologica Italiana 28:33-107.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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