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Lopes J.F.S.,Campus Universitario Of Martelos | Ribeiro L.F.,Campus Universitario Of Martelos | Brugger M.S.,Campus Universitario Of Martelos | Brugger M.S.,Laboratorio Of Insetos Sociais Praga | And 3 more authors.
Sociobiology | Year: 2011

Ant nests vary in their depth and internal complexity. They can be shallow or reach seven meters down into the soil, with many chambers connected by tunnels. In the case of leaf-cutting ants, the nest protects the colony and provides appropriate microclimate conditions for the ants and the symbiotic fungus garden. In the present study we compared the internal architecture and population size of Acromyrmex subterraneus molestans nests in an urban and a rural area. We excavated, molded and measured six nests in an urban area and five nests in a rural area. For each nest, we measured the total volume of fungus in the chambers and estimated the population by counting the workers, which were separated into four size classes. The nests of A. subterraneus molestans in the urban and rural areas were always found near the base of trees. In the urban area they were also found near the curb of sidewalks. Ants use old roots and debris to reinforce the structure of the nest tunnels and at the same time reduce the costs of excavation by taking advantage of pre-existing cavities. Nests from the rural area had only one chamber, whereas in the urban area they had up to four chambers. Fungus chambers showed non-defined shapes and were found near the soil surface, both in the urban and in the rural area. Closeness to the surface may pose a problem to the maintenance of the humidity levels required by the fungus garden. The accumulation of cut leaves over the nest, as observed for other species of leaf-cutting ants, in particular A. crassispinus, may be a strategy to solve this problem. Building superficial nests also helps reduce the costs of excavating, and saves energy in the transport of substrate to the fungus chamber. The nest tunnels were located in pre-existingcavities and almost always connected the external environment to the fungus chamber. There were also longer tunnels that opened at some distance from the nest. These tunnels allow an increase in the foraging area and reduce the risk of outside prédation. With respect to population size, we noted that the small workers represented on average 50% of the population, with no difference between the proportion of workers of each size class between urban and rural nests. No significant differences were found in the volume of fungus between nests of the urban and rural area. There were no significant correlations between the volume of fungus and the total population of workers or the number of workers of each size class.

Camargo R.S.,Federal University of Juiz de fora | Lopes J.F.S.,Federal University of Juiz de fora | Forti L.C.,Laboratorio Of Insetos Sociais Praga
Ciencia Rural | Year: 2013

The knowledge of the workers energy content is essential to measure the energy availability for maintenance and performance of activities essences for the colony growth. But little is known about the workers energy content, and how much will be available to carry out activities, for example, the excavation of the nest. The present study determined the lipid content and energy content of the worker ants inactive before and after excavation activity. Through the lipids determination, it can be calculated the energy content of workers resting (standing) with those which excavated. The lipid content and energy content of the workers were on average 9.1±0.8% and energy content of the workers was on average 111.31±54.71J, respectively, however, the experimental series did not differ significantly. Additionally, catabolic flux rate based in workers body mass was 14.76±10.11μW. It was concluded that the energy resource for the excavation of the nest is not coming from reserve lipid body, and thus the energy content of the workers did not change before and after excavation activity.

Forti L.C.,Laboratorio Of Insetos Sociais Praga | Rinaldi I.M.P.,São Paulo State University | Da Silva Camargo R.,Laboratorio Of Insetos Sociais Praga | Fujihara R.T.,Laboratorio Of Insetos Sociais Praga
Psyche | Year: 2012

We present a detailed description of the predatory behavior of the beetle Canthon virens Mannerheim, 1829, on the leafcutter ant Atta sp. We observed 51 acts of predation, which were also recorded on film and subjected to behavioral analysis. Canthon virens exhibited 28 behaviors while predating upon Atta sp. queens. Adult beetles search for queens while flying in a zigzag pattern, 15 to 20cm above the ground. After catching a queen, the predator stands on its back and starts cutting the queen cervix. Once the prey is decapitated, the predator rolls it until an insurmountable obstacle is reached. The distance from the site of predation to the obstacle can vary widely and is unpredictable. The beetle rolling the queen also buries it in a very peculiar way: first, it digs a small hole and pulls the queen inside, while another beetle is attached to the prey. The burial process takes many hours (up to 12) and may depend on the hardness of the soil and the presence of obstacles. In general, one or two beetles are found in a chamber with the queen after it is buried. They make the brood balls, which serve as food for the offspring. This study contributes to the knowledge of the predatory behavior of Canthon virens, a predator poorly studied in Brazil and widespread in the country. Copyright © 2012 Luiz Carlos Forti et al.

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