Myrmicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Queen lateral view (reduced, original).
Brazil (type locality), Costa Rica. Costa Rica: widespread in lowland wet forest, including the Osa Peninsula, San Vito area at 1200m, Manuel Antonio, Carara, La Selva Biological Station and surrounding Atlantic slope sites to 600m, Penas Blancas Valley, and the Pitilla area of Guanacaste Conservation Area.
Worker: first gastral tergum devoid of erect setae; postpetiolar dorsum irregularly rugose, without a raised subtriangular boss, and with more than 10 erect setae; mesosomal dorsum with irregular short rugae. Queen: first gastral tergum with about 50 or more long erect setae, relatively dense anteriorly, becoming sparser posteriorly, being replaced by extremely short appressed setae barely visible on the polished surface; postpetiole dorsum irregularly rugose, without raised subtriangular boss medially; Weber's length less than 1mm.
Similar species: haskinsi.
Workers and queens occur in samples of sifted leaf litter from the forest floor.
The type locality is southern Brazil. I examined USNM syntypes. The syntype worker I examined differed from Costa Rican material in having a lower petiolar node and the posterior face of the node rugose. In other sculptural, pilosity, and shape features they are a close match. The syntype queen I examined similarly differed in petiole shape, and also had a single erect hair on the first gastral tergite, instead of the 50 or more seen on Costa Rican queens. Costa Rican plaumanni shares petiole shape with haskinsi.
Using the name plaumanni for the Costa Rican material is a matter of convenience, given the overall phenetic similarity with the syntypes. I have no information on the reproductive continuity of Costa Rican and Brazilian Lachnomyrmex, or whether the various characters used to define Lachnomyrmex species are apomorphic, plesiomorphic, or homoplaseous.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. firstname.lastname@example.org
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