Postmating changes in cuticular chemistry and visual appearance in Ectatomma tuberculatum queens (Formicidae: Ectatomminae).

In the ectatommine ant Ectatomma tuberculatum, the visual appearance of queens changes after mating and ovarian development in that their cuticle turns from shiny to matte. In this study, we have shown that this change seems to be caused by 15-fold accumulation of hydrocarbons, in particular heptacosane that covers the multiple grooves present on the cuticular surface creating a wax coat in mated fully fertile queens. Analyses of the scrapped wax revealed that it is composed largely of heptacosane. Peak-by-peak comparison of the cuticular hydrocarbon (CHC) composition of mated, virgin with developed ovaries and virgin with nondeveloped ovaries revealed significant differences between the queen groups. Although the total amount of the CHC of virgin queens with developed ovaries was not higher than virgin queens that did not have developed ovaries, the composition showed a shift toward the mated queen. While it is possible that the large accumulation of hydrocarbons may give extra physical and chemical protection to queens, we propose that the switch in the relative abundance of heptacosane and nonacosane and perhaps of other components is indicative of being a mating and fertility cue. This is the first report in social insects where external chemical changes are accompanied by changes in visual appearance.

Comportamento e estrutura reprodutiva da formiga Dinoponera lucida Emery (Hymenoptera, Formicidae) / Behavior and reproductive structure of the ant Dinoponera lucida Emery (Hymenoptera, Formicidae)

A formiga Dinoponera lucida (Ponerinae), espécie endêmica da Mata Atlântica (Bahia, Espírito Santo e Minas Gerais), está incluída na lista de espécies ameaçadas do Brasil. O presente estudo teve por objetivo conhecer aspectos da sua biologia, em particular do seu comportamento, visando subsidiar o plano de manejo permitindo a conservação da espécie. Foram estudadas cinco colônias coletadas no município de Belmonte, Bahia, através do método scan sampling. A divisão de trabalho entre as operárias parece depender da idade dos indivíduos (polietismo etário) e organiza-se em dois grupos principais: operárias que cuidam da prole e operárias forrageadoras. A análise da espermateca apontou a ocorrência de uma única "gamergate" (operária com os ovários desenvolvidos e a espermateca funcional, que acasala e põe ovos fertilizados) por colônia (monoginia). Interações agonísticas incluem comportamentos peculiares, tais como: encurvamento do gáster, boxe antenal, mordida de mandíbula e imobilização. Essas interações foram observadas no geral com uma freqüência baixa, mas se mostraram mais comuns numa colônia sem gamergate. Em colônias com uma gamergate, esta não participa de nenhuma interação agonística. O entendimento dos mecanismos de reprodução, assim como das relações interindividuais, é extremamente importante para futuras ações de manejo onde qualquer tentativa de manipulação de colônias visando reinstalação ou reabilitação de uma população passa por esse tipo de conhecimento prévio.

The ant Dinoponera lucida (Ponerinae), endemic of the Atlantic rain forest (States of Bahia, Espírito Santo and Minas Gerais), is included in the list of Brazilian threatened species. We investigated aspects of its biology, particularly its behavior, to furnish arguments for a plan of management aiming the conservation of this species. Five colonies collected at Belmonte, Bahia, were studied through the scan sampling method. The division of labor between workers seems to depend on the individual age (age polyethism) and was organized in two groups: workers taking care of the offspring (nurses) and foragers. The spermatheca analysis pointed out the occurrence of a single "gamergate" (worker that have the ovaries developed and its spermatheca functional, able to mate and lay fertilized eggs) per colony (monogyny). Agonistic interactions included specialized behaviors, such as: gaster rubbing, antennal boxing, mandible bite and immobilization. These interactions were observed generally with a low frequency, but were more frequent in a colony with no gamergate. In colonies with a gamergate, this one does not participate in agonistic interactions. The understanding of reproduction mechanisms, as well as that of inter-individual relations, is extremely important for future management actions where any colony manipulation aiming at reinstallation or rehabilitation of a population needs this previous knowledge.