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)

Digging effort in leaf-cutting ant queens (Atta sexdens rubropilosa) and its effects on survival and colony growth during the claustral phase

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

Lipid and energy contents in the bodies of queens of Atta sexdens rubropilosa Forel (Hymenoptera, Formicidae): pre-and post-nuptial flight

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dyed baits distribution in nests of Atta sexdens L.. (Hym., Formicidae)

Dyed baits distribution in colonies of Atta sexdens was studied so as to test the hypothesis of uniform distribution. Three medium- to large-size (34-90 m(2)) colonies were used for the experiment; coloured dyed baits material was made available at the foraging orifices, which had previously been mapped out and grouped into three hypothetical sectors. After 24 h the colonies were killed and the nests excavated; the fungus was removed from each of the chambers for observation of the presence or absence of dyed baits. It was shown that coloured material from each of the different sectors was found in all the fungus chambers, thus confirming the hypothesis.

Substrate distribution in fungus chambers in nests of Atta bisphaerica Forel, 1908 (Hym., Formicidae)

Substrate distribution was studied in three adult colonies of the leaf-cutting ant Atta bisphaerica Forel, 1908 using dye. Some supply holes were mapped using baits made from small plastic straws impregnated with citric pulp. Two holes, equidistant from one another, were then selected in each nest. The colonies were excavated completely 24 h after bait placement. During excavation, fungus chambers were checked for dye. We observed that the dyed baits were distributed in all sectors and at all depths regardless of where the baits had been placed. This supported the hypothesis that toxic baits placed in a single supply hole are uniformly distributed throughout the colony.

Nesting biology and fungiculture of the fungus-growing ant, Mycetagroicus cerradensis: New light on the origin of higher-attine agriculture

The genus Mycetagroicus is perhaps the least known of all fungus-growing ant genera, having been first described in 2001 from museum specimens. A recent molecular phylogenetic analysis of the fungus-growing ants demonstrated that Mycetagroicus is the sister to all higher attine ants (Trachymyrmex, Sericomyrmex, Acromyrmex, Pseudoatta, and Atta), making it of extreme importance for understanding the transition between lower and higher attine agriculture. Four nests of Mycetagroicus cerradensis near Uberlandia, Minas Gerais, Brazil were excavated, and fungus chambers for one were located at a depth of 3.5 meters. Based on its lack of gongylidia (hyphal-tip swellings typical of higher attine cultivars), and a phylogenetic analysis of the ITS rDNA gene region, M. cerradensis cultivates a lower attine fungus in Clade 2 of lower attine (G3) fungi. This finding refines a previous estimate for the origin of higher attine agriculture, an event that can now be dated at approximately 21-25 mya in the ancestor of extant species of Trachymyrmex and Sericomyrmex.

Nest architecture of Pachycondyla striata Fr. Smith, 1858 (Formicidae, Ponerinae)

Nine nests of Pachycondyla striata Fr. Smith, 1858 were excavated between 2006 and 2007 at the UNESP university campus in Rio Claro, SP, southeastern Brazil. The P. striata population was larger in the two nests excavated in the months of August and November, 2006. The nests of this species are simple and poorly elaborated, with chambers and tunnels close to the ground surface. P. striata places the pupae in chambers isolated from the other individuals. The lack of chambers with the specific purpose of conditioning food and garbage underscores the simplicity of these nests.

Life Expectancy and Entropy Values for Workers of Pachycondyla striata (Hymenoptera: Formicidae: Ponerinae)

We investigated the life expectancy and entropy value for workers of the ant Pachycondyla striata. Seven nests were excavated and these colonies were raised in laboratory conditions. The workers have a mean life-span of 74.48 days, these have a high mortality rate in the period of 1 to 85 days with a high entropy value of H = 0.611, confirming the number of deaths in the initial period.

O jardim de fungo atua como um molde para a construção das câmaras em formigas cortadeiras?

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

DISTRIBUIÇÃO DE SUBSTRATOS NAS COLÔNIAS DE Atta laevigata (F. Smith, 1858) (HYMENOPTERA: FORMICIDAE)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nest architecture of the leaf-cutting ant Acromyrmex rugosus rugosus

The prominent nests mounds of many ant species are one of the most obvious signs of their presence, yet the subterranean architecture of nests is often poorly known. The present work aimed to establish the external and internal structure of nests of a species of leaf-cutting ant, Acromyrmex rugosus rugosus, by either marking the interior of nests with talcum powder, or forming casts with cement. Twelve nests were excavated and surveyed, with eight being marked with talcum powder and four cast with cement. The external and internal structure of the nests was highly variable. The largest and smallest nests had mound areas of 9.89 m(2) and 0.01 m(2) respectively. The number of chambers found ranged from I to 26, with maximum dimensions of between 6 and 70 cm. Chambers were found close to the soil surface (6 cm) down to a maximum depth of 3.75 m. In addition to chambers containing fungus garden, some chambers were found to be empty, filled with soil or filled with waste, the first time this has been recorded in a species of Acromyrmex. The nests of A. rugosus rugosus appear to be unusually complex for the genus, containing a diversity of irregular chambers and tunnels.

Nest architecture of Atta laevigata (F. Smith, 1858) (Hymenoptera : Formicidae)

The internal structure of three nests of Atta laevigata was studied in Botucatu city, São Paulo State, Brazil. Two nests were excavated through the opening of trenches and one was cement-moulded to enable a better view of the internal structures. The three nests presented a similar structure, with the depths and number of chambers varying as a function of the loose soil area of the nests. The number of chambers ranged from 1149 to 7864, reaching as deep as 7 m underground. Chamber volume ranged from 0.03 to 511. The foraging tunnels extended as far as 70m from the loose soil region. The nests of this species are the deepest within the genus Atta and have the highest number of chambers.

Multifractal characterization of saprolite particle-size distributions after topsoil removal

Multifractal analysis is now increasingly used to characterize soil properties as it may provide more information than a single fractal model. During the building of a large reservoir on the Parana River (Brazil), a highly weathered soil profile was excavated to a depth between 5 and 8 m. Excavation resulted in an abandoned area with saprolite materials and, in this area, an experimental field was established to assess the effectiveness of different soil rehabilitation treatments. The experimental design consisted of randomized blocks. The aim of this work was to characterize particle-size distributions of the saprolite material and use the information obtained to assess between-block variability. Particle-size distributions of the experimental plots were characterized by multifractal techniques. Ninety-six soil samples were analyzed routinely for particle-size distribution by laser diffractometry in a range of scales, varying from 0.390 to 2000 mu m. Six different textural classes (USDA) were identified with a clay content ranging from 16.9% to 58.4%. Multifractal models described reasonably well the scaling properties of particle-size distributions of the saprolite material. This material exhibits a high entropy dimension, D-1. Parameters derived from the left side (q > 0) of the f(alpha) spectra, D-1, the correlation dimension (D-2) and the range (alpha(0)-alpha(q+)), as well as the total width of the spectra (alpha(max) - alpha(min)) all showed dependence on the clay content. Sand, silt and clay contents were significantly different among treatments as a consequence of soil intrinsic variability. The D, and the Holder exponent of order zero, alpha(0), were not significantly different between treatments; in contrast, D-2 and several fractal attributes describing the width of the f(alpha) spectra were significantly different between treatments. The only parameter showing significant differences between sampling depths was (alpha(0) - alpha(q+)). Scale independent fractal attributes may be useful for characterizing intrinsic particle-size distribution variability. (c) 2006 Elsevier B.V. All rights reserved.

Comparação entre parâmetros externos e internos de ninhos de Atta bisphaerica Forel, 1908 (Hymenoptera, Formicidae)

Six Atta bisphaerica, Forel, 1908 (Hymenoptera, Formicidae) nests were excavated with the aim of studying the relationship between area and volume of the mound, the total volume and total number of chambers in the nest. Prior to excavation, the area and the volume of refused soil in the nests were measured. During excavation, all data referring to chambers were recorded, such as: length, depth and width. The nests named A1, A2, A3, A4, A5 and A6 presented 31.16; 40.87, 67.08, 35.04, 73.48 and 18,73m 2 of mound area, respectively. The mound area did not correlate either with the volume or with the total number of chambers. The mound volume correlated significantly with the mound area, total number and total volume of chambers. The total volume of chambers was correlated with the total number of chambers.

External and internal structure of Atta bisphaerica Forel (Hymenoptera: Formicidae) nests

This work was carried out to determine the internal and external structures of Atta bisphaerica (Forel) nests. Six nests were excavated and during excavation, all data referring to chambers and tunnels were recorded. Three nests had been internally cement-moulded, which enabled a better view of the chamber and tunnel structures. Atta bisphaerica nests presented a similar structural pattern, varying only in the number of chambers as a function of external mound area. Chambers were spherical with two communication tunnels. Internal tunnels had an elliptical section, sometimes circular, indirectly linked to chambers through ramifications and directly through short tunnels. Entrance holes were linked to the area of highest chamber concentration by tunnels from the elliptical section, which led to the nest in a radial manner. Knowledge of the colony's three-dimensional architecture permits successful application of chemical control processes, reduces the quantity of product applied, and consequently diminishes costs and environmental damage.