Trajectory of Water- and Fat-Soluble Dyes in the Grass-Cutting ant Atta capiguara (Hymenoptera, Formicidae): Evaluation of Infrabuccal Cavity, Post-Pharyngeal Glands and Gaster

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Behavior of Atta sexdens rubropilosa (Hymenoptera: Formicidae) workers during the preparation of the leaf substrate for symbiont fungus culture

The behavioral repertory of Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) workers marked by size category was studied during the preparation of the leaf substrate in the laboratory. The workers were marked according to three physical castes, i.e., minima, generalist and forager. Seven types of behavioral acts were recorded for each caste, with the following frequencies: licking leaf fragments (64.6%), holding fragments on the surface of the fungus garden (16.4%), shredding the fragments (6.0%), chewing and crimping the edges of the fragments (9.0%), incorporating the fragments (2.7%), touching the surface of the fungus with their mandibles and other mouthparts after incorporation (0.3%), and depositing fecal fluid (0.1%). The minima workers were found to be more specialized in the activities related to the preparation of the leaf substrate, which represented 52% of the total number of tasks performed. The generalists performed 40.3% of these tasks, and the foragers 7.9%. Licking the substrate was the behavior most frequently recorded and performed for a longer period of time. In this way, the workers may feed and at the same time eliminate microorganisms that are harmful to the symbiont fungus. The smaller castes, minima and generalists, are those most responsible for the preparation of the leaf substrate and predominate within a colony. From a practical viewpoint, with the introduction of toxic bait containing insecticides, for example, these size categories will be those most intensely intoxicated, especially through the behavior of licking bait pellets. On the basis of the data obtained about these behaviors, we may raise the hypothesis that trophallaxis in not the major factor triggering contamination with an insecticide among the workers of a colony.

Does diatomaceous earth control leaf-cutter ants (Hymenoptera: Formicidae) in the Eucalyptus plantations?

Genus Atta includes some of the most important Formicidae leaf cutter ants which cause extensive damage to the eucalyptus plantations. Atta sexdens rubropilosa Forel, one of the chief pests in Brazilian reforestation, can restrict and reduce forest productivity by its intense and constant leaf-cutting activities on plants at all stages. Therefore, the demand for new products to control A. sexdens rubropilosa indicates the study of the utilization of the dry powder formulation of diatomaceous earth (DE) against this pest in the eucalyptus cultivars. The study was conducted using 120 colonies of A. sexdens rubropilosa in Eucalyptus grandis Hill ex. Maiden x Eucalyptus urophylla Blake (Myrtaceae) (urograndis) stand. The randomized block experimental design was used with six treatments (1, 10, 25, and 50 g/m2 of DE, 6.0 g/m2 sulfluramid bait per square meter of loose soil, and the control) with five replications, each with four colonies of this ant. Diatomaceous earth was applied to the active A. sexdens rubropilosa ant holes, and the sulfluramid bait was applied in bulk in a localized manner. The control efficacy of A. sexdens rubropilosa with DE was low, showing values similar to that of the control, and, for this reason, it cannot be used to control this ant. The bait with sulfluramid showed higher efficacy than those of the other treatments.

Triterpene benzoates from the bark of Picramnia teapensis (Simaroubaceae)

Two new benzoic acid esters of triterpene alcohols [lup-20 (29)-en-28-oic acid 3 alpha, 7 beta -dibenzoate and 3 alpha -hydroxy-lup-20(29)-en-28-ic acid 7 beta -benzoate] were isolated from the stem bark of Picramnia teapensis Tul. The structures of these compounds were established on the basis of spectral analyses. Other known compounds, beta -sitosterol, estigmasterol, lupeol and epilupeol, were identified in mixture by GC-MS. The triterpene esters have not shown in-vitro inhibitory effect on the growth of Leucoagaricus gongylophorus (Fisher), referred also as Leucocoprinus gongylophorus (Heim), syn Rozites gongylophora (Moller), the symbiotic fungus cultivated by the leaf-cutting ant Atta sexdens L.

Occurrence of Atta laevigata (Hymenoptera: Formicidae) in the South of Espirito Santo State, Brazil. Recently Introduced or Endangered Species?

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Patogenicidade de isolados de três fungos entomopatogênicos a soldados de Atta sexdens sexdens (Linnaeus, 1758) (Hymenoptera : Formicidae)

As formigas cortadeiras atacam diversas culturas agrícolas, pastagens e os reflorestamentos, atuando sobre muitas espécies vegetais. O presente trabalho teve por objetivo avaliar a patogenicidade dos fungos Beauveria bassiana (isolados AM 9 e JAB 06), Metarhizium anisopliae (isolados E 9 e AL) e Paecilomyces farinosus (isolados CG 189 e CG 195) a soldados de Atta sexdens sexdens, em condições de laboratório. Após a coleta em formigueiro isento de produtos fitossanitários, exemplares de soldados foram cuidadosamente separados em grupos de oito indivíduos e, a seguir, banhados em suspensões contendo 1,0 x 10(6), 1,0 x 10(7), 1,0 x 10(8) e 1,0 x 10(9) conídios/mL de cada isolado. em seguida, cada grupo de formigas foi transferido para unidades de câmara úmida e mantido, sem alimentação, a 27 ± 1 ºC. A mortalidade foi verificada diariamente. Os três fungos se mostraram eficientes patógenos, pois provocaram alta mortalidade, matando mais que 80% dos soldados nos quatro primeiros dias após a inoculação. Os melhores isolados foram JAB 06 e AL, na concentração de 1,0 x 10(9) con./mL. Os isolados JAB 06, AL, CG 195 apresentaram maior capacidade de esporular nos cadáveres das formigas e os tempos letais decresceram com o aumento da concentração de conídios usada.

Behavioural responses of workers towards worker-produced male larvae and queen-produced worker larvae in Acromyrmex subterraneus brunneus Forel, 1911 (Hym., Formicidae)

Leaf-cutting ant workers care for larvae with an elaborate behavioural repertoire to satisfy the needs of the offspring. In order to investigate worker discrimination ability in the leaf-cutting ant Acromyrmex subterraneus brunneus, we compared the behavioural responses of workers towards worker-produced male larvae and queen-produced worker larvae, including the following behavioural acts: licking the larval body, transporting larvae, feeding larvae with hyphae, scraping larval mouth parts, ingesting faecal fluid excreted by the larva, and inserting hyphae of the symbiontic fungus on the larval body. We verified that workers behaved differently depending on larval origin, i.e. licking the larval body, transporting larvae and inserting hyphae of the symbiontic fungus on the larval body. Observed differences denote the ability of workers in discriminating among larvae, probably because of their different individual needs.

Physical resistance as a criterion in the selection of foraging material by Acromyrmex subterraneus brunneus Forel, 1911 (Hym., Formicidae)

Leaf-cutting ants forage on a wide variety of plant species using the physical and chemical characteristics of the plants as a selection criterion. In order to determine the influence of the physical factor on the selection of foraging material, inert materials such as floral sponge, polystyrene, plastic and clay, which possess different degrees of physical resistance to cutting, were offered simultaneously to five Acromyrmex subterraneus brunneus colonies, and assessed 12 and 24 h after foraging. No substrate selectivity was observed during foraging. Physical resistance was used as a decision criterion for the incorporation or return of the foraged material. This fact suggests the existence of a second time of selection of the foraged material inside the colony during cultivation of the symbiontic fungus.

The influence of the scout upon the decision-making process of recruited workers in three Acromyrmex species (Formicidae : Attini)

We examined how the information communicated by a scout worker influences the plant species transported by recruited workers in Acromymex balzani, Acromyrmex rugosus, and Acromyrmex crassispinus, three species of leaf-cutting ant that have different substrate and habitat preferences. We verified that certain plant species were more likely to be transported than others and that recruitment occurs. We found that recruited workers were more likely to transport non-preferred plant species when they were recruited to these by scout workers. The results suggest that the scout worker can communicate information about plant identity to recruited workers, but that recruited workers integrate the information communicated with their own experience during the decision-making process. (C) 2004 Published by Elsevier B.V.

Susceptibility of the ant-cultivated fungus Leucoagaricus gongylophorus (Agaricales : Basidiomycota) towards microfungi

The aim of this study was to select virulent strains of microfungi against Leucoagaricus gongylophorus, a symbiotic fungus cultivated by leaf-cutting ants. The results from in vitro assays showed that microfungal strains had a variable and significant impact on the colony development of L. gongylophorus. Specifically, Trichoderma harzianum, Escovopsis weberi CBS 810.71 and E. weberi A088 were more effective, inhibiting the L. gongylophorus colonies by 75, 68 and 67%, respectively (P < 0.05) after 15 days. Strain E. weberi A086 and Acremonium kiliense were less effective: 43 and 26%, respectively (P < 0.05). In spite of the current negative perspective of a microbiological control approach for these ants, the present work discusses the possibility of using mycopathogenic fungi for the control of these insects, and points out the importance of encouraging more studies in this area.

Relationship Between Population Size and Symbiont Fungus Culture Volume in Colonies of Acromyrmex balzani (Hymenoptera: Formicidae)

In order to quantify the population of Acromyrmex balzani Emery, 1890 nests and to verify whether the population dynamic of the colony is correlated with the symbiont fungus volume, the principal energy source of the colony, five nests located in grassland areas were evaluated. The nests were sprayed with neutral talcum powder to improve visualization and digging. The symbiont fungus and the entire population existent in the chambers were collected. The mean fungus volume and total nest population in excavated nests were, respectively, 74.76 ml and 1,095 individuals. Simple linear correlation analysis verified that the fungus volume grew proportionally to the number of individuals. Despite the correlation between fungus volume and population dynamic of colonies, the factors that determine this relationship are little known since other microorganisms live in association with the colony.

Internal Architecture and Population Size of Acromyrmex subterraneus molestans (Hymenoptera, Formicidae) Nests: Comparison Between a Rural and an Urban Area

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Growth of populations and the fungus garden of Atta sexdens rubropilosa (Hymenoptera, Formicidae) response to foraged substrates

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

Nota sobre a biologia de "Microdon tigrinus" (Diptera: Syrphidae), parasito social de "Acromyrmex coronatus" (Hymenoptera: Formicidae)

The fly of the syrphid Microdon tigrinus is a specific social parasite of leaf-cutting ant, Acromyrmex coronatus. Six colonies of Acromyrmex coronatus were collected in plastic containers, which there was a layer of 1 cm of plaster, with the purpose of maintaining the humidity of fungus culture. Larvae of social parasite were separate for the establishment of instars number, through morphometric study. The data were measured of 165 larvae, using spiracle (length (Ls), width (Ws) and distance between spiracle (Ds)). After that, the morphometric data obtained for the larvae were submitted to cluster analysis by Wong's hybrid method, which produces the adequate number of groups through pseudo F-statistics and pseudo t-squared statistics. The three morphometric variables studied permitted grouping of larvae into the following three distinct groups: cluster 1 [long dash] consisting of 55 larvae (Ls=0.177[plus or minus]0.026, Ws=0.163[plus or minus]0.030, Ds=0.052[plus or minus]0.008 mm); cluster 2 - consisting of 20 larvae (Ls=0.631[plus or minus]0.065, Ws=0.630[plus or minus]0.049, Ds=0.065[plus or minus]0.018 mm); cluster 3 - consisting of 90 larvae (Ls=1.294[plus or minus]0.062, Ws=1.308[plus or minus]0.069, Ds=0.140[plus or minus]0.018 mm). of the all couples, only 1 obtained success in the mating, and the female, after 24 hours, began the oviposition. The female layed 76 eggs in a period of 6 days, after that, her death. The larvae emerged in the seventh day (incubation period [plus or minus] 7 days). From 76 eggs, 54 were viable, with a viability of 71.05%. This study contributes to the knowledge of Microdon tigrinus biology of, a social parasite poorly studied in Brazil.

Aloetismo em Acromyrmex subterraneus brunneus Forel (Hymenoptera, Formicidae), durante o forrageamento, cultivo do jardim de fungo e devolução dos materiais forrageados

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