Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Costa Rica (Monteverde, Braulio Carrillo National Park at 1500m).
Color red black; sides of head above eyes moderately angular; face with median strip slightly impressed, punctatorugose, devoid of ground pilosity; scapes with differentiated, longer setae on leading edge; anterior lobe of scape weakly developed (SLL/SL 0.11); face with 18 specialized setae, 8 forming a double arc from eye to eye, behind this a straight row of 4, lacking an outer pair near the margin at the widest point of the head, and behind this a row of 6 on the posterior vertex margin; specialized hairs of face spatulate, diminishing in size in middle and anterior row, becoming less differentiated from ground pilosity; ground pilosity concentrated on vertex lobes, appressed to suberect; promesonotal dorsum evenly arched, propodeal suture distinctly impressed, propodeal dorsum subhorizontal, not forming a continuous curve with promesonotum; promesonotum usually with two pairs of specialized setae, one pair on humeri and one pair at midlength; specialized setae of promesonotum and gaster usually thin, nearly filiform; propodeal spines well developed, subtriangular; HW 0.75, HL 0.69, SL 0.40, SLL 0.05, WL 0.82 (n=1).
Variation: traits vary in directions towards nearby parapatric forms schmidti, JTL-008, and JTL-009, suggesting possible introgression. The anterior scape lobes are sometimes more developed; a very weakly differentiated specialized seta pair is sometimes present at the widest point of the head, similar to schmidti; occasionally only one pair or three pairs of setae occur on the promesonotum; occasionally the promesonotal setae are weakly clavate, approaching schmidti.
Similar species: schmidti, JTL-008, JTL-009, JTL-010.
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 abundant in the Monteverde cloud forest. It is also known from one Winkler sample from montane wet forest at 1500m on the north slope of Volcan Barba. In Monteverde, it is very tightly associated with the narrow band of cloud forest on the ridge crest, showing sharp parapatric boundaries with JTL-008 and JTL-009 on the Atlantic slope, and schmidti on the Pacific slope.
This species keys to gravis in Brown and Kempf (1960).
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.email@example.com
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