Estimates of Foraging Population and Territory of Heterotermes tenuis Colonies using Mark-Release-Recapture (Isoptera: Rhinotermitidae)

Heterotermes tenuis is an important economic pest in São Paulo state. Foraging populations of three field colonies of H. tenuis located on a University campus (UNESP, Rio Claro, SP, Brazil) were characterized. Foraging populations of H. tenuis colonies were calculated using four cycles of a mark-release-recapture program with a weighted mean method. The foraging population sizes of three colonies: A, B and C were 389,313±14,907; 265,589 ±12,635; and 641,600∓12,127; respectively. Foraging biomasses were 0.77 kg in the colony A, 0.51 kg in the colony B and 1.17 kg in colony C. Mean worker biomass was approximately 1.9 mg. Foraging territories occupied an area ranging from 70 m2 to 131 m2 per colony. The maximum linear foraging distance traveled by H. tenuis was 28m.

Foraging Behavior and Subtask Hierarchical Structure in Acromyrmex spp. (Hymenoptera: Formicidae)

This study considers the function and complexity of tasks during foraging of three Acromyrmex species. Foraging was classified as a team task composed of 2 or 3 processes: recruitment, selection, and collection. Each process was subdivided into different subtasks. Points were attributed to subtasks considering their hierarchical level to compare the complexity of foraging among species. Total scores obtained were 19 for A. balzani and 14 for A. crassispinus and A. rugosus, indicating different degrees of social complexity for grass-cutting and leaf-cutting ant species. Acromyrmex balzani, a grass-cutting ant species, shows a behavioral repertoire composed of more variable subtasks during foraging.

Non-Specific Interaction between Ants (Hymenoptera; Formicidae) and Fruits of Syagrus romanzoffiana (Arecaceae) in an Area of the Brazilian Atlantic Forest

On the forest floor of a fragment of the Atlantic Forest which is considered to be in a stage of recuperation, located in southeastern Brazil, we recorded 54 species of ants interacting with the fruits of Syagrus romanzoffiana (Arecaceae). Myrmicinae was the subfamily which was the richest in species, followed by Ponerinae, Formicinae, Ecitoninae, Dolichoderinae, Pseudomyrmecinae and Cerapachyinae. The fruits of S. romanzoffiana can be classified according to whether or not they are preyed by the squirrel Sciurus ingrami, and the ant fauna that visits the fruits has an average similarity. Regarding diversity, the data suggest that there is no significant difference between ant assemblages at preyed and non-preyed-upon fruit falls. The results also indicate that there is no specific interaction between the ant fauna that visits the fruits of S. romanzoffiana, as it consists largely of species with omnivorous feeding habits.

Juvenile Hormone Effect on the Venom Gland Secretory Cycle in Workers of Apis mellifera (Hymenoptera, Apidae)

The present investigation analyzed the influence of Juvenile Hormone (JH) on the venom glands of Apis mellifera workers through protein dosage and electrophoresis of venom gland extracts of newly emerged workers which were treated with 1 μl JH dissolved in hexane, in concentration of 2μg/μl. Newly emerged workers non-treated and treated with 1 μl hexane were the controls. Both JH and hexane provoke quantitative changes on the gland protein titre and on the protein electrophoretic profile. The disappearance of protein bands in the venom gland extracts of 14 day-old treated workers, a situation normally found only in 35 day-old non-treated workers, suggests that the JH treatment induces a precocious maturation of the worker venom gland.

Male behavior in colonies of the social wasp Polistes lanio (Hymenoptera, Vespidae)

Sixteen post-emergent colonies of Polistes lanio were studied while producing males in the course of the colonial cycle. Individually, they remained in the nest only 10.5 days (5-31, n=165). Twelve different male behaviors were observed: remaining immobile on the nest (82,8%), giving alarm (4,8%), flying out from the nest (2,4%), copulating on the nest (2,4%), being dominated (1,6%), self-grooming (1,2%), checking cells (1,2%), adult-adult trophallaxis (receiving food) (0,8%), larva-adult trophallaxis (0,8%), chewing prey and giving it to the larvae (0,8%), returning to the nest without food (0,8%), and fanning the nest (0,4%). In comparison to the behavioral repertory of females (28 items), they performed fewer tasks and remained immobile most of the time on the nest. Their behavior was largely related to self maintenance, but also included giving chewed prey to the larvae, giving alarm signals and fanning the nest.

The ant (Hymenoptera: Formicidae) community in two species of the Euphorbiaceae, Alchornea sidifolia and Croton floribundus, in an area of the Atlantic Forest of Brazil

The number of individuals and species richness of ants were investigated in two species of Euphorbiaceae found in three areas of differentiated flora. These areas form part of a fragment of the Atlantic Forest located in the Serra do Itapety, in the state of São Paulo, Brazil. Fifty eight ant species were sampled, belonging to 23 genera and 6 sub-families; 40% of the species are arboreal. The sub-family Myrmicinae was the richest in species, with Pheidole being the most diverse genus and Crematogaster the most commonly-occurring. In the three study areas, no significant differences were found between the number of individuals and the species richness of ants collected on the trunks of Euphorbiaceae. C. floribundus Spreng and A. sidifolia Muell. Arg. are similar with respect to the number of ant species sampled; the number collected being 40 and 47, respectively.

Dominance hierarchy in different stages of development in colonies of the primitively eusocial wasp Mischocyttarus cassununga (Hymenoptera, Vespidae)

Seven colonies of Mischocyttarus cassununga were studied under field conditions at Universidade Federal de Juiz de Fora, MG, in southeastern Brazil: in pre-emergence, post-emergence and decline stages, during 145.8 hours. Dominance interactions among the females were quantified to verify the dynamics of succession in the social hierarchy of the colonies. Early pre-emergence colonies present more intense aggressive interactions than late pre-emergence ones, because the females are engaged in securing the role of main egg layer in the nest. In post-emergence (pre-male) colonies the dominance hierarchy is more defined and the frequency of dominance and subordination behaviors were lower than in pre-emergence stages: most of the agonistic behaviors are restricted to the first ranked females (potentially queens) and the subordinate individuals play the role of workers in the nests. In the post-emergence, post-male, and decline stages the hierarchy is still maintained by the aggressive behaviors of the 1st-ranked female but because the presence of males and future nest foundresses these interactions are not well defined in a linear way.

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.

The influence of fruit morphology and habitat structure on ant-seed interactions: A study with artificial fruits

Artificial fruits designed to simulate lipid-rich non-myrecochorous diaspores were used to test for the effect of fruit morphology and habitat structure on ant-seed interactions in an Atlantic Forest site in SE Brazil. The outcome of the interaction (i.e., if the fruit was removed, cleaned by ants on the spot or had no interaction with ants) and the time of ant response were the investigated variables. Models simulating drupes and arilate diaspores were used to test for morphological effects and four habitat attributes (litter depth, number of logs, number of trees, and percentage of bromeliad coverage on the forest floor), likely to be correlated with the ant diversity and abundance in the study site, were measured to test for the effect of habitat structure. The proportion of fruits removed or cleaned did not differ between the two morphological models. Sites in which fruits were cleaned had more trees than those in which no interaction occurred. This may be a result of the foraging behavior of arboreal ants that frequently descend to the forest floor to exploit fleshy diaspores. Sites in which model removal occurred had lower litter depth than both those in which models were cleaned and those in which no interaction occurred. A negative correlation was observed between litter depth and ant response time. Accumulation of leaf litter at a given point may have constrained the movements of large ants in general, and ponerine ants (that are important seed removers) in particular. We conclude that that local pattern in litter depth and tree density influence the frequency and outcome of interactions between ants and non-myrmecochorous, fleshy diaspores.

Toxicity of sesame extracts to leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Extracts of different sesame plant (Sesamum indicum, Linnaeus) organs were tested through ingestion and contact experiments to investigate their toxicity to Atta sexdens rubropilosa (Forel) workers. Dichloromethane extracts of seeds were toxic to the leaf-cutting ants and the factor responsible for the toxicity does not show seasonal occurrence.

Note about the first swarming in a laboratory colony of Coptotermes gestroi (Isoptera: Rhinotermitidae)

A laboratory rearing of Coptotermes gestroi which swarmed from the reared colony is described.

Toxicity of sesame seed to leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Extracts of the ripe seeds of the sesame plant (Sesamum indicum, Linnaeus) were tested through contact experiments to investigate their toxicity to Atta sexdens rubropilosa workers. Dichloromethane extract of seeds was toxic to the ants and the factor responsible for this effect was distributed through the ethyl acetate fraction. This fraction was divided into four sub fractions composed of: A) triglycerides, B) monoglycerides + diglycerides + triglycerides, C) diglycerides + sesamoline + sesamine and D) sesamine. However, when these sub fractions were separated, no toxicity was observed. Therefore, in order to determine why the activity was lost, the concentration of each sub fraction was duplicated, and the possible combinations among them were also tested. We concluded that the toxicity to the ants is due mainly to a mixture of triglycerides, and sesamoline or the combination of sesamoline + sesamine can be a synergistic factor in this fraction.

Astilbin toxicity to leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

The toxicity of astilbin, isolated from Dimorphandra mollis, was tested in laboratory ingestion bioassays for the leaf-cutting ant Atta sexdens rubropilosa Forel. Worker ants that were fed an artificial diet daily to which astilbin was added had a higher mortality rate than the controls. The substance astilbin was incorporated into the diet with and without the utilization of a solvent. Results for both methodologies utilized were similar and indicate that astilbin reduces the median survival of ants. All concentrations tested showed toxic effects against ant workers, and the statistical comparison of survivorship rates from control and treated groups was significantly different, confirming the insecticidal properties of the substance astilbin.

Temporal polyethism and survivorship of workers of Agelaia pallipes (Hymenoptera, Vespidae, Epiponini)

In this study, known-age workers of Agelaia pallipes (Olivier) were introduced into a colony maintained in the laboratory and the effects of age polyethism on the worker life span were observed. As in other Neotropical swarm-founding wasps, the results showed that younger workers remained on different places inside the nest performing activities related to the brood and nest maintenance, while risky tasks such as foraging were performed by older workers. Furthermore, the start of foraging activities had a significant effect on worker mortality.

Toxicity of Cedrela fissilis to Atta sexdens rubropilosa (Hymenoptera: Formicidae) and its symbiotic fungus

Crude extracts from roots, stems, branches, fruits and leaves of Cedrela fissilis were tested to verify their toxicity to Atta sexdens rubropilosa workers and to their symbiotic fungus Leucoagaricus gongylophorus. The workers that were fed daily on an artificial diet to which crude extracts from this plant were added had a higher mortality rate than the controls, especially for the hexane, dichloromethane and methanol crude extracts from roots (RH, RD and RM) and from leaves (LH, LD and LM). Fungal growth was inhibited by the hexane (RH) and dichloromethane crude extract from roots (RD). The RH, RD and FD crude extracts were fractioned and their fractions were tested. All the fractions tested presented toxicity to the ants and some fractions (RH-H, RH-D, RD-4 and RD-5) completely inhibited fungus development. The possibility of controlling these insects in the future using Cedrela fissilis compounds that can simultaneously target both organisms is discussed.