The fungus-growing ants (Tribe Attini) are a New World group of > 200 species, all obligate symbionts with a fungus they use for food. Four attine taxa are known to be social parasites of other attines. Acromyrmex (Pseudoatta) argentina argentina and Acromyrmex (Pseudoatta) argentina platensis (parasites of Acromyrmex lundi), and Acromyrmex sp. (a parasite of Acromyrmex rugosus) produce no worker caste. In contrast, the recently discovered Acromyrmex insinuator (a parasite of Acromyrmex echinatior) does produce workers. Here, we describe a new species, Acromyrmex ameliae, a social parasite of Acromyrmex subterraneus subterraneus and Acromyrmex subterraneus brunneus in Minas Gerais, Brasil. Like A. insinuator, it produces workers and appears to be closely related to its hosts. Similar social parasites may be fairly common in the fungus-growing ants, but overlooked due to the close resemblance between parasite and host workers.
As formigas cortadeiras dos gêneros Atta e Acromyrmex possuem grande especialização na construção de ninhos. Estes se constituem da parte externa, caracterizada pela presença de terra solta e/ou, substrato vegetal seco e da parte interna, composta por câmaras (panelas) e túneis (canais) escavados no solo pelas operárias. Orifícios ligam a parte externa à interna. Existem câmaras para o cultivo do fungo simbionte, onde são alojados também os ovos, larvas, pupas e adultos, e câmaras para o lixo que contêm formigas mortas, fungo exaurido e vegetal seco. Em Acromyrmex spp., a área externa do ninho pode ser formada por terra solta ou não. Algumas espécies apresentam a área externa coberta por palha ou fragmentos vegetais. Os ninhos de Acromyrmex geralmente são inconspícuos, dificultando sua localização (Della Lucia & Moreira 1993).Acromyrmex rugosus rugosus tem larga distribuição geográfica, sendo encontrada, em áreas de cerrado e caatinga em quase todo o País, podendo afetar culturas como algodão, feijão e laranja; além de plantas silvestres como pau-ferro (Gonçalves 1961
-Social parasites exhibit several characteristics that allow them to exploit their host species efficiently. The smaller size of parasite species is a trait commonly found in ants. In this work, we investigated several aspects of the reproductive biology of Acromyrmex ameliae De Souza, Soares & Della Lucia, a recently discovered parasite of Acromyrmex subterraneus subterraneus Forel. Sexuals of A. ameliae are substantially smaller than those from host species. Parasite queens laid significantly less worker eggs than host queens and inhibit sexual production of the host. The sex ratio of parasite species is highly female biased. Interestingly, we have observed parasite coupling on the laboratory, inside the nests and in the ground, opening the possibility to use controlled mating to study genetic approaches of parasitism in the ants.
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