Eurhopalothrix schmidti (Menozzi 1936)

Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

worker lateral view

worker face view


Costa Rica (Monteverde, Meseta Central, Talamanca range).


Monteverde and Fila Cruces specimens: color red black; sides of head above eyes moderately angular; face rugose; scapes with differentiated, longer setae on leading edge; anterior lobe of scape moderately well developed (SLL/SL 0.17); face with 20 specialized setae, 8 forming a double arc from eye to eye, behind this a straight row of 6, the outermost ones near the margin at the widest point of the head, and behind this a row of 6 on the posterior vertex margin; specialized hairs on face spatulate, uniform in size, erect, distinct from smaller ground pilosity; ground pilosity small, sparse, evenly distributed on face; promesonotal dorsum evenly arched, propodeal suture distinctly impressed, propodeal dorsum subhorizontal, not forming a continuous curve with promesonotum; promesonotum usually with one pair of spatulate specialized hairs on humeri, occasionally one or two additional unpaired setae posteriorly; propodeal spines well developed, subtriangular; gastral dorsum with spatulate specialized hairs; HW 0.80, HL 0.77, SL 0.45, SLL 0.07, WL 0.89 (n=1).

Pittier Biological Station specimens: on some of the specimens in this series, the specialized setae of the middle row of the face are reduced or absent.

Similar species: JTL-001, JTL-008, JTL-009, JTL-010.

Natural History

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 relatively abundant in the Monteverde community area, from 1300-1500m on the Pacific slope. This is a moist forest transition zone between the dry forest habitat lower down and the perpetually wet cloud forest on the ridge crest. The type locality is "La Caja," a site on the Meseta Central between the airport and San Jose. It was presumably a moist forest area at the time of collection, in the 1930's. I have also seen the species at two montane sites in southern Costa Rica. At the Pittier Biological Station, a site at 1670m on the Pacific slope of the central talamancan Cordillera, I encountered it in a Winkler sample from a patch of mature forest near a pasture edge. I also found it in a Winkler sample from a forest patch on Fila Cruces, a 1200m site near Wilson Botanical Garden.

Type Data

Rhopalothrix (Rhopalothrix) schmidti Menozzi 1936:82. Syntype worker, queen, larva: Costa Rica, La Caja [8km W. San Jose] (Schmidt) [MCZC, DEIC] (DEIC worker examined). Synonymized under E. gravis by Brown and Kempf 1960. PROPOSED REVISED STATUS.

I examined a type worker in 1990, and my notes indicate that it was identical to specimens from my collection #1487-s, a Winkler sample from "Hogue's Woods" in Monteverde.

Taxonomic notes

In the key of Brown and Kempf (1960), this species would fail at couplet 2 because it has 20 rather than 18 specialized setae on the face. Otherwise it keys to gravis, the species under which it was synonymized.

Literature Cited

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.

Menozzi, C. 1936. Due nuovi Dacetini di Costa Rica e descrizione della larva di uno di essi (Hymenoptera: Formicidae). Arb. Morphol. Taxon. Entomol. Berl.-Dahl. 3:81-85.

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.

Page author:

John T. Longino, The Evergreen State College, Olympia WA 98505

Date of this version: 29 October 1999
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