A pest is a pest is a pest? The dilemma of neotropical leaf-cutting ants: Keystone taxa of natural ecosystems

Leaf-cutting ants of the genera Acromyrmex and Atta are considered the principal polyphagous pests of the Neotropics. Although some members of these genera are of economic importance, have a broad geographic distribution, and are extremely good colonizers, others are endemic and closely interact with native ecosystems. Control is generally practiced against any colony, irrespective of its taxonomic status. Indiscriminate control coupled with habitat destruction threatens endemic species with extinction, and, through habitat simplification, favors other pest species. As nests of Atta are large, having several square meters of nest surface, the endemic taxa can be easily used as environmental indicators for natural ecosystems. Likewise, the pest species can be used to detect environmental disturbance. As these ants are keystone species and easily identified by nonspecialists, efforts should be made to integrate these into viable conservation programs.

Fungus-growing ants (Hymenoptera: Formicidae) on Santa Catarina Island, Brazil: patterns of occurrence

A taxonomic survey on fungus-growing ants (Attini) was made at 14 beaches on Santa Catarina Island (SC), Brazil. The samplings were manual, in soil or litterfall, in the following habitats: sandy beach, herbaceous vegetation and shrubby vegetation. From 12 species of Attini (ten of Acromyrmex Mayr and two of Cyphomyrmex Mayr), the most frequent were Cyphomyrmex morschi Emery and Acromyrmex crassispinus Forel, collected, respectively, on eight and ten of the monitored beaches. Altogether, Sorensen's similarity coefficients were high (range: 0.59-0.80), in spite of the lower numbers of ant species on sandy beaches.

The effect of plant diversity on fungus garden development and foraging behavior of leaf-cutting ants (Hymenoptera: Formicidae)

The leaf-cutting ants forage a wide variety of plant species, used for symbiotic fungus cultivation. To better understand this tripartite complex interaction, 24 colonies of Acromyrmex subterraneus brunneus were conditioned for 4 months to 6 different plants (Citrus spp., Ligustrum spp., Acalypha spp., Eucalyptus spp., Alchornea triplinervia, Melia spp.), to verify the influence of conditioning on foraging behavior of workers. The effect of plants on symbiotic fungus development was studied separately, through macerated plants in Agar and culture medium A as the control. During foraging, workers presented polyphagic foraging behavior, refusing the plants to which they were conditioned. The selection of plants is not correlated with the plant substrate that promotes good development of symbiotic fungus. Such results demonstrate the importance of plant diversity for fungus garden maintenance.

Method for the evaluation of insecticidal activity over time in Atta sexdens rubropilosa workers (Hymenoptera: Formicidae)

The active ingredients used in the formulation of toxic baits for leaf-cutting ants (Hymenoptera: Formicidae) should possess a delayed action defined as an insecticidal activity whereby worker mortality is ≤15% at 24 hours and ≥90% at 21 days. Serious shortcomings have occurred in the search for new active ingredients, such as the initial selection of fenoxycarb, copper oxychloride and diflubenzuron, compounds considered very promising but whose inefficiency was verified only later, indicating methodological problems. In view of this situation, we developed a classification method for insecticidal activity over time using workers of the leaf-cutting ant Atta sexdens rubropilosa Forel. The insecticides used were fipronil, sulfluramid GX071HB and sulfluramid GX439, vehicled in an attractive pasty formulation prepared based on citrus pulp. The results obtained were consistent from a toxicological viewpoint and agreed with the literature in terms of the control of colonies. Sulfluramids were found to possess a delayed action at a broad range of concentrations, in agreement with the fact that these substances are highly effective in the control of all leaf-cutting ant species. The smaller range of concentrations of fipronil with delayed action is probably related to its lower efficacy for species more difficult to control such as Atta capiguara (Forti et al. 2003). We discuss the importance of relating behavioral particularities to the specific feeding habits of leaf-cutting ants, with methodological adequacy of the assessment of insecticides aimed at toxic baits.

Comparative study of the fat body in some genera of the attini tribe (Hymenoptera: Formicidae)

The Cyphomyrmex rimosus Spinola and Mycetarotes parallelus Emery species of ants, considered basal, and Acromyrmex disciger Mayr and Atta laevigata Smith, considered derived, have fat bodies specially distributed on their gaster, around their organs and right below the cuticle. The fat body is formed by trophocytes, which are characterized by their pronounced vacuolization of the cytoplasm and the irregular morphology of their nuclei caused by the pressure exerted by cytoplasmic vacuoles. In C. rimosus, the nuclei are more regular, presenting an oval or a star form. In A. disciger and A. laevigata the nuclei present chromatin in a cord form, while in C. rimosus and M. paralellus the chromatin is uniformly distributed in the nucleoplasm, very condensed in the latter species. The parietal trophocytes of A. disciger show cytoplasm with a smaller quantity and smaller sizes of vacuoles compared to ones from the perivisceral region, the opposite is observed in C. rimosus. In A. laevigata and M. parallelus there were no differences observed in their cytoplasm between both regions of cells. In the trophocytes of C. rimosus, A. disciger, A. laevigata, there was a reticular aspect of the cytoplasm observed in the region between vacuoles, not seen on M. parallelus. Another cellular type, oenocyte, was found associated with the fat body cells, and is dispersed between trophocytes with an inner contact to them, but no membrane fusion with them. The oenocytes have a spherical form and are smaller than the trophocytes; they have acidophilic cytoplasm with a small quantity of small vacuoles, and round nuclei.

Ant fauna (Hymenoptera: Formicidae) in Magnoliophyta native to the Atlantic forest

The aim of the study was to analyze the preferences of ant species visiting the trunks of eight species of Magnoliophyta, belonging to the families Fabaceae, Arecaceae, Myrtaceae, Melastomataceae and Euphorbiaceae, located in a fragment of the Atlantic Forest in southeastern Brazil. A total of 101 ant species, belonging to eight subfamilies and 32 genera, were sampled during the 12-month collection period. Close to 30% of the ant species can be considered arboreal, and the others are species that nest in the ground and use trees only for foraging, which can be occasional, as in the case of the Ecitoninae sampled in Arecaceae and Euphorbiaceae. Pachycondyla mesonotalis was the only species collected on all the Magnoliophyta, whereas Camponotus rufipes, Acromyrmex niger and Crematogaster spp., were found on 87.5% of the trees analyzed. No strong similarities were found, using the Jaccard Index, among plant species in the same family of Magnoliophyta based on the visiting ants, except for the Euphorbiaceae species. This result is probably related to the presence of extra-floral nectar, which is very attractive to ants and characteristic of this family.

Leveduras isoladas de ninhos de formigas da tribo Attini (Hymeniptera: Formicidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Respostas comportamentais de operárias de Atta sexdens rubropilosa forel, 1908 (hymenoptera, formicidae) a substâncias voláteis

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Análise morfológica comparativa da estrutura do corpo gorduroso nos Attini em diferentes níveis filogenéticos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

O papel dos microfungos associados aos jardins das formigas Attini (Hymenoptera: Formicidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evolução e metabolismo de alguns atíneos (Hymenoptera: formicidae) e seus fungos simbiontes (Basidiomycota: agaricales)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Desenvolvimento de iscas atrativas para a formiga cortadeira de gramíneas Atta capiguara Gonçalves, 1944 (Hymenoptera, formicidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudos toxicológicos de princípios ativos utilizando como modelo Atta sexdens rubropilosa (Hymenoptera, formicidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evolução dos comportamentos de preparação do substrato para o cultivo do fungo simbionte e cuidados com a cria, rainha e alados em formigas da tribo Attini (Hymenoptera: Formicidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Semioquímicos e comunicação sonora em formigas cortadeiras (Hymenoptera: Formicidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)