Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Costa Rica (Monteverde, southern Talamanca range at 1670m).
Color red orange; sides of head above eyes strongly angular; face uniformly punctate, overlain with faint longitudinal rugulae; scapes with differentiated, longer setae on leading edge; anterior lobe of scape well developed (SLL/SL 0.26); 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 strongly clavate to pompon-like, uniform in size, erect, distinct from ground pilosity; ground pilosity conspicuous and subdecumbent to appressed and nearly invisible, when visible abundant on much of face, especially laterally and anterolaterally, uniformly covering clypeus; mesosomal dorsum evenly arched, propodeal suture weakly impressed, promesonotum and propodeum forming continuous curve; promesonotum with three pairs specialized hairs; propodeal spines well developed, triangular; first gastral tergite with 4 pairs of clavate setae, underlain with conspicuous appressed spatulate ground pilosity; HW 0.67, HL 0.63, SL 0.39, SLL 0.10, WL 0.66 (n=1).
Similar species: gravis.
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 4 Winkler samples from the 1350-1500m moist forest zone of Monteverde, and from 2 Winkler samples from a patch of mature forest at 1670m, Pittier Biological Station in the southern Talamanca range.
This species is very similar to alopeciosa Brown and Kempf (1960), differing mainly in its larger size and more angular lateral margins of the head (judging from the description of alopeciosa).
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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