Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Costa Rica (19km S Ciudad Neily).
Color orange; sides of head above eyes weakly angular; face uniformly punctate; scapes uniformly covered with appressed spatulate setae, without differentiated, longer setae on leading edge; anterior lobe of scape strongly developed (SLL/SL 0.31); specialized hairs of face pompon-like, on single specimen posterior row of specialized hairs 3 on one side, 2 on the other; middle row with one seta on one side, none on the other; anterior row with 2 outer setae on each side (could be typical 18 with some lost due to wear, or could typically lack median setae in middle and anterior rows); specialized hairs uniform in size, erect, distinct from smaller ground pilosity; ground pilosity of appressed, spatulate hairs, sparser medially; mesosomal dorsum evenly arched, propodeal suture not impressed; promesonotum with three pairs pompon hairs; propodeal spines moderately developed, with broad, translucent flange extending almost perpendicularly down from tip of spine; gastral dorsum with pompon hairs, underlain by conspicuous spatulate ground pilosity; HW 0.55, HL 0.56, SL 0.37, SLL 0.11, WL 0.55 (n=1).
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 Winkler sample from 19k S Ciudad Neily, a lowland rainforest site near Golfo Dulce, in a patch of mature rainforest.
This species keys to alopeciosa in Brown and Kempf (1960), but differs from it in a number of features. It is clearly related to a group of small species that includes alopeciosa from Trinidad, clypeata from Guyana, and pilulifera from Mexico. They all share small size, specialized setae large and pompon-like, ground pilosity strongly spatulate and conspicuous, and anterior scape lobe strongly developed. Like pilulifera, JTL-005 has the ground pilosity relatively evenly distributed over face, without a bald spot under the specialized setae, it lacks ground pilosity on the clypeus, and the propodeal spines are subrectangular rather than tooth-like. Unlike pilulifera, it has a short head like clypeata and alopeciosa (CI 98), and the sides of the head are somewhat angular.
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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