Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Images of alternate worker: face view (small image, large image); lateral view (small image, large image).
Costa Rica (Atlantic slope wet forest).
Gastral dorsum with at most one pair of spatulate setae a little over half way back, and a cluster near the apex; labrum deeply notched with lateral lobes rounded; side of head with only median gibbosity projecting (where the transverse ridge attains the side of the head), giving a subtriangular aspect.
The genus Rhopalothrix is a member of the monophyletic tribe Basicerotini (Bolton 1998). I assume that Rhopalothrix share the predaceous habits of other members of the tribe. The few basicerotines whose habits are known prey on small, soft-bodied arthropods (Wilson 1956, Brown and Kempf 1960, Wilson and Brown 1985).
I know this species from two locations: La Selva Biological Station and the Penas Blancas Valley. At La Selva, I have seen specimens from 6 Project ALAS Berlese samples, 1 Project ALAS Malaise trap sample, and 1 Winkler sample. At Penas Blancas, I have seen a specimen from 1 Winkler sample.
The relatively high frequency in Project ALAS Berlese samples, which are soil plugs to 10cm deep, and the paucity in the many Winkler samples from La Selva and Penas Blancas, suggest that this species nests in the soil and does not forage in the leaf litter. The nearly eyeless condition suggests subterranean foraging, but the one specimen from a Malaise trap is intriguing.
Rhopalothrix weberi Brown and Kempf 1960:234. Replacement name for Heptastruma wheeleri Weber 1934:55. Holotype (unique syntype) worker: Cuba, Cienfuegos, Central Soledad, Casa Harvard (Weber) [Weber collection?].
Although I have not seen the type of weberi, the general aspect of Weber's figure (in the 1934 paper), the deeply bilobed labrum, the small size, and the distribution of spatulate setae on the gaster all match the Costa Rican form.
Bolton, B. 1998. Monophyly of the dacetonine tribe-group and its component tribes (Hymenoptera: Formicidae). Bulletin of the Natural History Museum London (Entomology) 67:65-78.
Brown, W. L., Jr., Kempf, W. W. 1960. A world revision of the ant tribe Basicerotini. Stud. Entomol. (n.s.) 3:161-250.
Weber, N. A. 1934. Notes on neotropical ants, including the descriptions of new forms. Rev. Entomol. (Rio J.) 4:22-59.
Wilson, E. O. 1956. Feeding behavior in the ant Rhopalothrix biroi Szabo. Psyche (Camb.) 63:21-23.
Wilson, E. O., Brown, W. L., Jr. 1985 ("1984"). Behavior of the cryptobiotic predaceous ant Eurhopalothrix heliscata, n. sp. (Hymenoptera: Formicidae: Basicerotini). Insectes Soc. 31:408-428.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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