Results 1 - 10 of 130
Results 1 - 10 of 130. Search took: 0.021 seconds
|Sort by: date | relevance|
[en] The fauna of beetles (Coleoptera: Carabidae) and ants that survive in the soil of a passion fruit crop under conventional management in Roldanillo-Valle del Cauca was examined, in March and May (rainy season) and in June and July (dry season), 2012. We carried out four samplings of monthly intensity in two plots with plants of different ages, and registered the species found. We found 149 individuals of Carabidae, distributed into ten species and 2447 ants, distributed in 19 morphospecies. The most abundant species of ants was Solenopsis geminata, while Megacephala (Tetracha) sobrina was the most abundant species of Carabidae. It was also found that the abundance and richness of carabid beetles tend to be higher in the rainy season, while some ant species showed a preference for specific seasonal periods. We conclude that a rich fauna of ground carabids and ants survives in the study area, which could contribute in the control of phytophagous insects populations associated with the crops of passion fruit.
[en] The process of urbanization of natural environments has dramatically increased the incidence of pest insects. To control these organisms in urban environments, the last decades have been marked by an increase in the use of synthetic insecticides. However, the intensive and indiscriminate use of synthetic insecticides has provoked a series of environmental problems and human health. In this way, the concern and the searching for environmentally safer alternatives for the control of urban pests is increasing. In the present study we evaluated the lethal and sublethal effects of essential oils (EOs) of six accessions of Varronia curassavica (Jacq.) (Cordiaceae) and their constituents (E)-caryophyllene and α-humulene on the ant Dorymyrmex thoracicus Gallardo, 1916 (Formicidae: Dolichoderinae), a species commonly found in urban environments and which can cause damage to human health. Bioassays of fumigation toxicity and locomotor activity in partially treated arenas were performed. The lethal concentrations to kill 50% of the D. thoracicus population ranged from 0.69 to 2.48 μL/L for EOs and from 3.75 to 1.49 μL/L for the (E)-caryophyllene and α-humulene compounds. The survival of the ants exposed to LC95 of the treatments was reduced over time, ranging from 4.2 to 35.6 h to kill 50% of the D. thoracicus population. In general, EOs of V. curassavica caused repellency and affected the locomotor activity of the ants. Our results indicate that EOs of V. curassavica are a promising source for the control of the urban ant D. thoracicus.
[en] Competitive ability and numerical dominance are important factors contributing to the ability of invasive ant species to establish and expand their ranges in new habitats. However, few studies have investigated the impact of environmental contamination on competitive behavior in ants as a potential factor influencing dynamics between invasive and native ant species. Here we investigated the widespread contaminant selenium to investigate its potential influence on invasion by the exotic Argentine ant, Linepithema humile, through effects on reproduction and competitive behavior. For the fecundity experiment, treatments were provided to Argentine ant colonies via to sugar water solutions containing one of three concentrations of selenium (0, 5 and 10 μg Se mL−1) that fall within the range found in soil and plants growing in contaminated areas. Competition experiments included both the Argentine ant and the native Dorymyrmex bicolor to determine the impact of selenium exposure (0 or 15 μg Se mL−1) on exploitation- and interference-competition between ant species. The results of the fecundity experiment revealed that selenium negatively impacted queen survival and brood production of Argentine ants. Viability of the developing brood was also affected in that offspring reached adulthood only in colonies that were not given selenium, whereas those in treated colonies died in their larval stages. Selenium exposure did not alter direct competitive behaviors for either species, but selenium exposure contributed to an increased bait discovery time for D. bicolor. Our results suggest that environmental toxins may not only pose problems for native ant species, but may also serve as a potential obstacle for establishment among exotic species. - Highlights: • Argentine ant colonies exposed to selenium had reduced fecundity compared to unexposed colonies. • Viability of offspring was negatively impacted by selenium. • Queen survival was reduced in colonies treated with selenium. • Interference competition for both the invasive species and the native species was not impacted by selenium. • Selenium exposure contributed to an increase in bait discovery time by the native ant species, Dorymyrmex bicolor. - The findings of this study highlight the potential impacts of environmental contamination as a barrier in range expansion of invasive ant species.
[en] The efficiency and palatability of two baits were studied to the control of crawling insects in urban areas: 'Cockroach Kill Gel' for control of cockroaches and Faratox B for control of ants. Ionizing energy was used in producing the baits. It was concluded, that after irradiation the palatability of Faratox B improved and palatability of Cockroach Kill Gel did not change
[en] Termites are major pests of crops and forestry in tropical and sub-tropical regions of Africa and Asia. Until recently, they were controlled by organochlorine (cyclodiene) insecticides whose persistence protected the crops till harvest and exotic trees through the susceptible seedling stage. These insecticides have been banned or withdrawn from use in agriculture in most countries and existing alternative insecticides lack the persistence to provide protection against termites. Controlled release formulations of some of these short-lived insecticides have been shown to provide protection for trees and crops as good as that provided by the cyclodiene insecticides without the environmental problems. Current formulations are much more expensive than conventional formulations using the same active ingredient and their use is limited to high value crops and forestry. (author). 21 refs, 3 figs, 2 tabs
[en] A new technique for tracing the dispersal of seeds by ants is described. At a site in the Sierra Nevada Foothills, California, Cytisus scoparius seeds were hand-painted with coloured fluorescent paint, placed in seed depots and the place of relocation by ants was discovered at night using an UV lamp. The technique worked best in areas with sparse vegetation and little litter, whereas in dense vegetation it became too time-consuming. It is suggested that recovery of seeds would be much lower in habitats where vertebrate seed predation is common
[en] The species of ants and Ground beetles at Olkiluoto in Eurajoki were studied in the summer of 2008 during two trapping periods: in June and August. The research goal was to clarify the species on Olkiluoto island of the earlier mentioned groups, at least at the family level, and to collect samples for further examination by Posiva. The trapping areas were selected at Olkiluoto in Posiva test monitoring sectors, a part of the trapping areas was the same as the earlier study. Species of ants, depending on their particular species, are a very dominating group of insects. The ants are the most important predators, scavengers and soil movers in Finnish forests. It looks as if the biomass of ants may be more than 10% of the biomass of all animals in certain areas of Finnish forests. In Finland there are about 60 species of ants that have been observed. They have been divided into four sub-groups, which are Myrmicinae, Formicinae, Ponerinae and Dolichoderinae. In Finland there are close to 300 species of ground beetles (Carabidae), which are divided into dozens of different families. The species, to a great extent, consist mostly of predatory insects that prey on microbes in field layers, but a part of them are specialized in feeding on flora. Ground beetles are usually divided into three groups according to their choice of habitat: Species that favour open biotopes, species that favour forests, and generalist species that can thrive in a variety of environments. Ground beetles also reflect changes in their living environment, and possibly they can be significant as socalled bio-indicators. Pitfall traps were used as the method of research. The preservative fluid used was ethanol (50%) with dishwashing liquid to remove surface tension. The points were located in various different biotopes in fields, meadows and forests. The data collected was defined as a minimum for the family level of Ground beetles and for ants to the species or species pairs. The species of Ground beetles and ants found in the pitfall trap study represented a quite usual range of species for southern Finland and no rare or endangered species were detected amongst the individuals defined to their particular species. The number of individual ants appeared to be higher in biotopes that were predominantly forested with conifers but as far as the amount of species was concerned, the dispersion between different biotopes was great. The amounts of species and individuals concerning the ground beetles were higher in open field-and meadow habitats. The differences in sizes amongst the ground beetles are remarkable. The weight of a large individual Carabus hortensis is the same as the weight of several individuals of smaller species together. These species, together with Pterostichus niger and Patrobus atrorufus, make up the majority of the communities of ground beetles in Olkiluoto, both in numbers and in weight. (orig.)
[en] This paper proposes a technique aiming to compute all global minimizers, while avoiding local minimizers, through chaotic ant swarm (CAS) optimization method. This technique incorporates the recently proposed deflection and repulsion techniques to alleviate local minimizers. Those approaches can be used in combination with CAS to detect all global minimizers effectively. The performance of the algorithm is illustrated on test problems of global optimization. Experimental results indicate the effectiveness of the proposed algorithm.
[en] The identification problem of delay time as well as parameters of time-delay chaotic system is investigated in this paper. The identification problem is converted to that of parameter optimization by constructing suitable fitness function. A novel optimization method, called CAS (chaotic ant swarm), which simulates the chaotic behavior of single ant and the self-organization behavior of ant colony, is used to solve this optimization problem. Illustrative example demonstrates the effectiveness of the proposed method.
[en] The phenotypic diversity of ant workers plays a fundamental role in their biology. In this study, we asked if the body size variation of monomorphic workers of the ant Lasius niger (Formicidae) responds adaptively to metal pollution in a post-mining metal-polluted area. Nest samples of workers were collected along a pollution gradient to calculate the within-colony variance in body size (expressed as maximum head width, HW). The results showed that the body size variation of L. niger was unrelated to the pollution index but demonstrated considerable variation between colonies even within the same study site. We suggest that the differences in morphological diversity between the colonies of L. niger could be shaped by colony personality traits, i.e., by colony-specific foraging and/or the feeding efficiency of nursing workers. The study supports previous findings, showing that morphological traits in Lasius ants are weakly related to environmental metal pollution.