Bioecological and behavioral interaction between pollinating bees and the pioneer shrub Ludwigia nervosa in degraded area suggests an exotic bee as its major pollinator

The flowers of plants of the genus Ludwigia are an important source of food for several species of bees. In the current study, we conducted an experiment with the aim to describe the reproductive biology and phenology of L. nervosa; to identify the species of visiting bees; analyze the foraging behavior of bees; and to investigate whether the reproductive success of the species is related to the foraging activity of bees. We found that the flowers received visits from several native bee species (n = 7), in addition of the exotic honey bees which came to be the dominant species. During visits the majority of the bees foraged in both resources, pollen and nectar. The significantly higher production of fruits in open pollinated pollination experiment compared to artificial cross pollination, suggests honey bees as effective pollinator of this plant species in the study site. Pollen deposition occurs efficiently, given the absence of pollen limitation. Despite massive visitation of honey bees, Ludwigianervosa is attractive to native bees, and therefore it may help to sustain population of both native and exotic pollinators in fragmented humid areas

Preliminary studies on the effects of d-limonene to workers of the leaf-cutting ant Atta sexdens rubropilosa and its implications for control

To better understand the potential of controlling of leaf-cutting ants, a serious pest, with conventional synthetic insecticides as well as botanical pesticides, we propose to evaluate the effect of d-limonene on attractiveness and rejection of citric pulp to the leaf-cutting ant Alto sexdens rubropilosa Ford. Five treatments were adopted that consisted of fragments of filter paper impregnated with various concentrations of d-limonene and with organic extract of citrus pulp. The number of fragments loaded by the ants in the foraging arena and transported to the fungus garden and of fragments rejected in the refuse chamber was counted. It has been shown that d-limonene provoked concentration-dependent reduction of attractiveness response to A. sal-dens rubropilosa workers. No rejection of loaded fragment was observed. We discussed the relationship between substrate selection and its repellent compounds, and also that a repellent substrate component can be overcome or masked by the overall odour of attractive substrates. Also, the repellence of the toxic bait Al (active ingredient) and its implication in control efficiency and the use of repellent Als in other control methods, emphasizing nebulization, are discussed.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Oviposition, Life Cycle, and Longevity of the Leaf-Cutting Ant Acromyrmex rugosus rugosus

Studies related to the demography of individual members from ant colonies have received little attention, although they are the basis to understanding the population dynamics of colonies. Thus, the objective of this work was to study the queen oviposition rate and the duration of the life cycle and longevity of Acromyrmex rugosus rugosus workers. To determine the oviposition rate, queens from three colonies were individually placed in plastic containers, and the eggs laid were quantified over a 96 h period. The development of the immature forms was observed every 24 h, with which the duration of each stage of development was determined. To verify the longevity of workers, the newly emerged adults were marked and daily observations were made. According to the results, there is variation in the development time of immature forms within the colony itself and between colonies. In addition, the number of eggs deposited was also inconstant in the three colonies, ranging from 5 to 119 eggs per day, while the longevity of workers varied from 3 to 7 months. Occasionally, it was found that the workers feed on the eggs produced by the queen; besides, there was a disappearance of larvae and pupae during the research, indicating a possibility of the practice of cannibalism in this species

Attractiveness of citrus pulp and orange albedo extracts to Atta sexdens rubropilosa (Hymenoptera: Formicidae)

The present study aimed to compare the attractiveness of industrial citrus pulp with the handmade orange albedo to the workers of Atta sexdens rubropilosa. For this, filter paper fragments were impregnated with organic extracts obtained through chemical extraction and sequential fractioning with hexane and dichloromethane and offered to different field nests. It was verified that the industrial citrus pulp extract is as good as the handmade orange albedo extract. This preference is discussed keeping in mind the chemical, behavioral and nutritional factors

Influence of Fungal Contamination on Substrate Carrying by the Leafcutter Ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Toxic baits are the most used method for controlling leafcutter ants and are usually composed of a mixture of dehydrated citric pulp with an active ingredient dissolved in soy oil. In this study, we evaluate if filamentous fungi and the water content of baits influence substrate carrying by Atta sexdens rubropilosa workers. First, we determined the prevalence of fungi on formulated baits composed of different pulp sources from commercial and noncommercial toxic baits. Fungal species such as Aspergillus niger, Paecilomyces sp., and Penicillium funiculosum were found on both kinds of bait, revealing that spores of such microbes are viable after the manufacturing process. Then, the formulated bait with the highest prevalence of fungi was presented to ants in four treatments: (1) sterilized dry bait, (2) sterilized wet bait, (3) non-sterilized wet bait, and (4) non-sterilized dry bait. Overall differences in substrate carrying among treatments were observed in the first presentation (24 h) in which no signs of fungal growth were visible on baits. Specifically, treatments 3 and 4 were the most carried and were significantly different from treatments 1 and 2 that were the least carried (p = 0.0154; F = 4.71). on the second and third presentation (48 and 72 h) baits with visible fungal growth and baits overgrown with fungi were presented to ants, respectively. All treatments were carried at the same level and no significant differences were observed. Pre-selected substrates with higher moisture content and without microbes in relation to substrates with massive microbial loads were expected to produce a negative response, however, both substrates were carried. This and other aspects of substrate carrying are discussed.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Influence of physical and chemical factors during foraging and culture of the symbiont fungus in Atta sexdens rubropilosa (Hymenoptera : Formicidae)

The aim of this paper is to investigate the influence of physical and chemical factors on transport and use of substrate for Atta sexdens rubropilosa workers. Three types of rectangular fragments were used to study the physical influence factors: filter paper with paraffin, filter paper without paraffin and polyester film. To study the chemical factors, some fragments were impregnated with organic extract of orange albedo, others were soaked with soybean oil and for the remaining ones nothing was applied. The following parameters were evaluated: (i) attractiveness of substrate for transport and number of loading workers per treatment; (ii) foraged material incorporation; (iii) rejection by numbers of fragments deposited in the garbage or beside the fungus garden. All the polyester film fragments carried out to the fungus garden were subsequently rejected. We verified that chemical factors of the substrate were more quickly detected by the workers, whereas physical factors were used as a criterion in the decision-making to reject or accept the substrate collected

Behavioral Response of the Leafcutter Ant, Atta sexdens rubropilosa (Hymenoptera, Formicidae), to Components of Citrus Pulp

Citrus pulp is an attractive substrate for dicotyledon-cutting ants, due to its physical and chemical properties. In this study, the behavioral response of Atta sexdens rubropilosa workers to different components of the fruit of Citrus sinensis was examined. The removal of these substrates was assessed by visual scanning in the laboratory and in the field. Six behaviors were recorded and the role of the olfactory stimulus in the choice of substrate was examined. Pellets of endocarp were the most collected and processed by workers, and licking the bait was the behavior with the highest average number of workers. The olfactory stimulus was important in the selection of the material, but it alone was not enough to recruit other individuals to the source.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Description and morphometry of the sting apparatus in the three worker casts of Acromyrmex subterraneus brunneus (Formicidae, Attini)

We studied the morphometry of the sting apparatus of Acromyrmex subterraneus brunneus workers by dissection and mounting of the structures on slides, and present here a brief description and illustrations. Sting apparatus examinations showed differences in size, but without morphological differences. The seven morphometric variables studied permitted grouping of the Ac. subterraneus brunneus workers into the following three groups: cluster 1 - consisting of 85, 39 large, 45 medium and 1 small workers; cluster 2 - consisting of 44 small workers, and cluster 3 - consisting of 6 large workers. This study demonstrated that all worker castes follow the same morphological pattern, although functional characteristics of the sting apparatus should be highlighted

Microscopic evidence supports the hypothesis of high cellulose degradation capacity by the symbiotic fungus of leaf-cutting ants

Leaf-cutting ants (Hymenoptera, Formicidae) use fresh leaf fragments to cultivate a symbiotic fungus (Basidiomycota, Agaricales) as their food source. There are three hypothetical propositions for the degree of cellulose degradation capacity of this symbiont: (i) that it is high, rendering this polymer an important energy source, as originally purposed by Martin and Weber; (ii) that it is very small, and only facilitates the symbiont to use other cell nutrients and, (iii) that this fungus is metabolically inept against this polymer. The two latter proposals are more recent than the first one but are based on in vitro or highly indirect evidence. Consequently, we carried out a new evaluation of the degradation capability of this fungus, utilizing as realistic an approach as possible by assessing the microscopic effect of fungus cultivation on the leaf anatomy of the grass Paspalum notatum within colonies of the grass-cutting ant Atta capiguara. We observed a complete degradation of the most abundant leaf cells (the non-lignified ones). on the other hand, since lignin-rich structures presented only slight damage, the leaf format was maintained. Therefore, this in vivo study corroborates Martin and Weber's hypothetical proposition: that cellulose is highly degraded by the leaf-cutting ant symbiont, thus serving as an important energy source.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq