Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Dorsal hairs of mesosoma and gaster not conspicuously plumose (at very high magnification, traces of branching can be seen, but side branches are extremely short; contrast with the conspicuously plumose hairs of JTL-002); postpetiolar dorsum regularly longitudinally costulate (contrast with the smooth postpetiole of JTL-001); basidorsal costulae of AT4 at least half as long as length of postpetiole (much shorter on JTL-001).
Panama, Costa Rica (to Mexico if versuta a junior synonym). Costa Rica: widespread in midmontane to lowland sites.
Hylomyrma workers and queens occur in samples of sifted leaf litter from the forest floor. Little else is known about them.
Kempf 1973 last revised Hylomyrma. Two very similar species were dentiloba, from Panama, and versuta, from Mexico and Belize. He had relatively little Central American material with which to examine character variation, and he suggested that further collecting might reveal continuous variation between the two forms. Several of the characters he used for species distinctions do vary considerably within Costa Rica, as follows.
Dorsal sculpture on mesosoma (Fig. 1, reduced, original). Material from the northern Atlantic lowlands, south to La Selva, and montane sites such as Penas Blancas, Braulio Carrillo National Park above La Selva, and San Vito, have transverse rugae on the anterior pronotum, and a fairly abrupt transition to more longitudinal rugae on the mesonotum. The rugae are variably distinct, with shiny crests emergent from the underlying striolate-punctate sculpture. Material from Rara Avis (a site just south and upslope of La Selva), Carara, and the Osa Peninsula have less organized sculpture, with short, lumpy rugulae overlain by the striolate-punctate sculpture. Material from Hitoy Cerere is intermediate. This is one of the main differentiating features for versuta (distinct rugae) and dentiloba (indistinct rugae). A transition seems to be occurring in Costa Rica, from more dentiloba-like traits in the south to more versuta-like traits in the north.
Sculpture on AT4. versuta and dentiloba varied in the length of the costulae radiating from the postpetiolar insertion. This trait seems highly variable in Costa Rica.
Relative narrowness of compound eye. This is highly variable in Costa Rica, and seems to span the differences used in couplet 10 of Kempf's key.
Sculpture of outer face of tibiae. Most Costa Rican dentiloba have faint traces of striation on tibiae. One specimen from Rara Avis has strongly striate tibiae.
I have chosen to use the name dentiloba for all the Costa Rican material in this group, since it is the older name.
Winkler and/or Berlese samples from La Selva Biological Station, Braulio Carrillo Nat. Park to 1000m, Rara Avis, Hitoy Cerere Biol. Res., Penas Blancas, Guanacaste Conservation Area (Pitilla), Wilson Botanical Garden, Carara Biol. Res., Osa Peninsula (Rancho Quemado).
Kempf, W. W. 1973. A revision of the Neotropical myrmicine ant genus Hylomyrma Forel (Hymenoptera: Formicidae). Studia Entomol. 16:225-260.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. email@example.com