Eurhopalothrix gravis (Mann 1922)

Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

worker lateral view

worker face view


Mexico, Honduras (type locality), Costa Rica (Atlantic lowlands), Dominica, Brazil (SC).


Color orange red; sides of head above eyes strongly angular; face rugose, with median carina; scapes with differentiated, longer setae on leading edge; anterior lobe of scape moderately developed (SLL/SL 0.17-0.24); 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, uniform in size, erect, distinct from smaller inconspicuous ground pilosity; ground pilosity evenly distributed on face; mesosomal dorsum evenly arched, propodeal suture weakly impressed, promesonotum and propodeum forming continuous curve; promesonotum with three pairs specialized hairs; propodeal spines short, broadly triangular; first gastral tergite with 4 pairs of clavate setae, underlain with sparse short appressed ground pilosity; measurements of two workers: HW 0.88, HL 0.77, SL 0.48, SLL 0.08, WL 0.89 (La Selva); HW 0.78, HL 0.70, SL 0.45, SLL 0.11, WL 0.80 (Penas Blancas).

Variation: the worker from Penas Blancas is smaller and has longer anterior scape lobes (thus approaching JTL-006). It also has only two specialized setae on the promesonotum, but this could be due to wear.

Similar species: JTL-006.

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.

I know this species from (1) a worker at the edge of the lab clearing at La Selva Biological Station, (2) a dealate queen under epiphytes in an old treefall at La Selva, and (3) a worker from a Winkler sample from Casa Eladio in the Penas Blancas Valley east of Monteverde. Brown and Kempf (1960) reported a collection of workers and alate queens from Limon Province, Hamburg Farm (F. Nevermann).

I also tentatively place under this species a dealate queen from a Winkler sample from Hitoy Cerere Biological Reserve. It is smaller than the La Selva queen, and differs significantly in sculptural details, but of all the species I currently recognize, it seems closest to gravis.

Type data

Rhopalothrix (Rhopalothrix) gravis Mann 1922:40. Syntype worker, queen, male: Honduras, Lombardia and San Juan Pueblo [USNM, MCZC].

Rhopalothrix reichenspergeri Santschi 1923:1263. Syntype worker: Brazil, Santa Catarina State, Blumenau [NHMW]. Synonymy by Brown and Kempf (1960).

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. I consider this to be a distinct species; see under schmidti.

Taxonomic notes

Brown and Kempf (1960) had a very broad interpretation of this species; my interpretation is narrower. However, the material I have examined from La Selva and Penas Blancas matches very closely Mann's original description and figures, and Brown and Kempf's figure.

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.

Mann, W. M. 1922. Ants from Honduras and Guatemala. Proc. U. S. Natl. Mus. 61:1-54.

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.

Santschi, F. 1923. Descriptions de quelques nouvelles fourmis du Bresil. Rev. Mus. Paul. 13:1255-1264.

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
Previous versions of this page:
Go back to top

Go to Ants of Costa Rica Homepage