Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Costa Rica (Osa Peninsula).
Color orange; sides of head above eyes relatively rounded, not strongly angular; face uniformly punctate; scapes with differentiated, longer setae on leading edge; anterior lobe of scape moderately developed (SLL/SL 0.18); face with 18 specialized setae, 8 forming a double arc from eye to eye, behind this a straight row of 4, and behind this a row of 6 on the posterior vertex margin; specialized setae on face pompon-like, uniform in size, erect, distinct from smaller ground pilosity; ground pilosity evenly distributed on face; mesosomal dorsum evenly arched, propodeal suture weakly impressed; promesonotum with three pairs pompon hairs; propodeal spines well developed, broadly triangular; first gastral tergite with several pairs of pompon setae; HW 0.57, HL 0.58, SL 0.35, SLL 0.06, WL 0.65 (n=1).
Very similar to bolaui; differs in propodeal suture less impressed, propodeal dorsum sloping, less differentiated from continuous curve of promesonotum, sides of head less angular above eyes, size slightly smaller, and color lighter red.
The genus Eurhopalothrix occurs in the Neotropics and in the Indo-Australian-southwestern Pacific area (Brown and Kempf 1960). They are members of the "cryptobiotic" fauna: small, slow ants that live in rotten wood and leaf litter. They are predators, preying on small, soft-bodied arthropods (Wilson 1956, Brown and Kempf 1960, Wilson and Brown 1985).
Workers and nests are extremely difficult to see in the field, because the workers are camouflaged and very slow moving. On disturbance they freeze, often curling into a pupal position, and remain motionless for several minutes (Wilson and Brown 1985, Hoelldobler and Wilson 1986). As a result of their cryptic nature, they were considered extremely rare until the 1960's. But increasing use of Winkler and Berlese sampling has shown Eurhopalothrix to be relatively common. I encounter them in most Winkler samples from wet forest sites in Costa Rica.
This species is known from one collection, a queen and a worker found under loose bark of rotten wood at San Pedrillo, in Corcovado National Park.
Brown, W. L., Jr., Kempf, W. W. 1960. A world revision of the ant tribe Basicerotini. Stud. Entomol. (n.s.) 3:161-250.
Hoelldobler, B., Wilson, E. O. 1986. Soil-binding pilosity and camouflage in ants of the tribes Basicerotini and Stegomyrmecini (Hymenoptera, Formicidae). Zoomorphology (Berl.) 106:12-20.
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.firstname.lastname@example.org
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