Wedson Desidério Fernandes

Occurrence of Diaretiella rapae (Mc´Intosh, 1855) (Hymenoptera: Aphidiidae) Parasitising Lipaphis erysimi (Kaltenbach, 1843) and Brevicoryne brassicae (L. 1758) (Homoptera: Aphididae) in Brassica napus in Mato Grosso do Sul

The occurrence of Diaretiella rapae parasitising Lipaphis erysimi and Brevicoryne brassicae in canola field (Brassica napus) was evaluated through two sample methods in Dourados-MS. The methods, used weekly, were: entomologic sweep net and plants sacking. The aphids population was observed from initial to the senescence plant development. Aphids were more abundant during the flowering phase, and they were usually located in the stems of the inflorescence and development fruits. In this phase the largest parasitism level for D. rapae (89,7%) occurred. The sample method with a sweep net captured significantly (t=4,484, P £ 0,01) more D. rapae while sacking method captured more parasitise aphids (t=2,199 with P £ 0,05) and active aphids (t=3,513, P £ 0,01).

Modelo arquitetônico de ninhos da formiga Ectatomma vizottoi Almeida (Hymenoptera, Formicidae)

The construction pattern and occupancy of Ectatomma vizottoi was described, during November 2004-August 2006 period, in Dourados, state of Mato Grosso do Sul by excavation of eight nests. The entrance openings, or exit, have an ellipsoid shape and lead to a wide tunnel, similar to a hall, which is connected to other deeper chambers in the nest. The nests reach up to 360 cm deep and contain three to ten chambers. Nests are constructed independently of plants and roots presence, and the soil of the tunnels and chambers are compacted, with specific compartments for colony deposit of detritus. The increase of the ant density led to an increase in nest depth and number of chambers, maintaining an average nest volume, which indicates a standard size for nest chambers.

Studies of the floral biology and reproductive system of Brassica napus L.(Cruciferae)

Studies of the floral biology of canola were accomplished with the objective of enlarging the system and reproductive strategies knowledge of its CTC-4 cultivar in Dourados, Centerwest, Brazil. Brassica napus is self pollinated, presenting however, many resources for the allogamy accomplishment, e.g., abundant pollen, nectar and scent production. The smaller anther were responsible for the production of fruit with smaller and less growth seeds, when compared to the autogamy, autopollination and cross pollination tests.

Colony cycle of the social wasp Mischocyttarus consimilis Zikán (Hymenoptera, Vespidae)

Colony cycle of the social wasp Mischocyttarus consimilis Zikan (Hymenoptera, Vespidae). This study describes some aspects of the colony cycle of the Neotropical social wasp Mischocyttarus consimilis, from data obtained under field conditions. Our results showed that the colony cycle in M. consimilis is annual and asynchronous in relation to the months of the year. The colonies remained active for approximately eight months. Most of the abandonments were associated with natural causes, and were most frequent in the pre-emergence stage. The nests were constructed preferentially in man-made structures, especially in sites protected from direct sunlight and rain. Colony foundation was either by haplometrosis or pleometrosis, being the first form predominant.

Nest Architecture, Colony Productivity, and Duration of Immature Stages in a Social Wasp, Mischocyttarus consimilis

Abstract This study examined the nest architecture, colony productivity, and duration of the immature stages of the social wasp Mischocyttarus consimilis Zikán (Hymenoptera: Vespidae). The study was carried out under field conditions. Nests of M. consimilis consist of a single uncovered comb, which is attached to the substratum by a single petiole. The data for the nest architecture showed a positive and significant correlation between the size of the comb and the diameter of the petiole, and also between the height and diameter of the cells. The nests were constructed on horizontal, vertical, and sloping substrata with no apparent preference for a specific orientation. The colonies produced 72.9 cells and 40.7 adults on average. The mean frequency of productive cells was 33.3%, and 19.4% of the cells were reused. The mean duration of the immature stages combined was 69.7 days and the egg, larval, and pupal stages had mean durations of 14.9, 36.0, and 18.8 days, respectively. The duration of each immature stage was significantly shorter in the warmhumid season, and the larval and pupal stages were shorter during the colony pre-emergence stage.

Temporal variation in the composition of ant assemblages (Hymenoptera, Formicidae) on trees in the Pantanal floodplain, Mato Grosso do Sul, Brazil

Temporal variation in the composition of ant assemblages (Hymenoptera, Formicidae) on trees in the Pantanal floodplain, Mato Grosso do Sul, Brazil. In this paper we investigate how seasonal flooding influences the composition of assemblages of ants foraging on trees in the Pantanal of Mato Grosso do Sul. During the flood in the Pantanal, a large area is covered by floods that are the main forces that regulate the pattern of diversity in these areas. However, the effects of such natural disturbances in the ant communities are poorly known. In this sense, the objective of this study was to evaluate the effect of temporal variation in assemblages of ants foraging on trees in the Pantanal of Miranda. Samples were collected during a year in two adjacent areas, one who suffered flooding during the wet period and another that did not suffer flooding throughout the year. In 10 sites for each evaluated habitat, five pitfall traps were installed at random in trees 25 m apart from each other. In the habitat with flooding, the highest richness was observed during the flooding period, while there was no significant change in richness in the area that does not suffer flooding. The diversity of species between the two evaluated habitats varied significantly during the two seasons. Most ants sampled belong to species that forage and nest in soil. This suggests that during the flood in flooded habitats, ants that did not migrate to higher areas without flooding adopt the strategy to search for resources in the tree canopy.

Predacious activity of Ants (Hymenoptera: Formicidae) in conventional and in No-till agriculture systems

This study had the objective of assessing the differences in foraging activity of the predacious ants between two areas, one conventional and other with no-till agriculture systems. The research was conducted in two contiguous 1.5 ha plots in Dourados MS, Brazil, from February 2001 to December 2003. Each plot received 750 baits (Nasutitermes termites), 425 at daylight and 325 at night. The termites were placed on the filter paper, on the ground, and ant attack was monitored for 15 min, until removed. Sixteen ant species were found in the no-till system and nine in the conventional system. Baits removed from no-till were significantly higher than the conventional plots and were influenced by the sampling time, at day or night. The seasons of the year did not significantly explain the variations in the structure of the predacious ant communities in neither of the systems. The significant differences at foraging activity and ant richness between the areas indicated that the no-tillage system could improve environmental quality of the cropping and therefore, became an important tool for the integrated pest management programs.

Atividade de alguns insetos em flores de Brassica napus L. em Dourados-MS e a interação com fatores climáticos

Objetivou-se estudar a flutuacao populacional, horarios de visitacao e a interacao com fatores climaticos de insetos visitantes de flores de Brassica napus L. em diversos estadios fenologicos. O trabalho foi realizado em Dourados, MS, Brasil. Os insetos foram coletados com rede entomologica de 30 cm de diâmetro, a cada duas horas, no periodo de 7 as 17 horas. Foram coletadas as abelhas Apis mellifera, Linnaeus, 1758, Trigona sp., o vespideo Brachygastra lecheguana (Latreille - 1824) e uma especie de Chloropidae (Diptera), que foi a mais abundante e frequente nas amostragens. O pico populacional da maioria dos insetos foi das 9 as 15 horas; contudo, para Trigona sp., foi entre 9 e 11 horas. A maior frequencia de insetos ocorreu durante o estadio fenologico III. A analise de correlacao evidenciou que a umidade relativa entre 11 horas (r = 0,57) e 13 horas (r = 0,43) favoreceu a ocorrencia do diptero da familia Chloropidae. Reducoes nas populacoes de insetos do estadio III para o IV foram devidas, provavelmente, a temperaturas mais baixas, que atingiram a media de 16,1oC.

Predation of Fruit Fly Larvae Anastrepha (Diptera: Tephritidae) by Ants in Grove

Based on evidence that ants are population regulatory agents, we examined their efficiency in predation of fruit fly larvae Anastrepha Schiner, 1868 (Diptera: Tephritidae). Hence, we considered the differences among species of fruit trees, the degree of soil compaction, and the content of soil moisture as variables that would explain predation by ants because these variables affect burying time of larvae. We carried out the experiment in an orchard containing various fruit bearing trees, of which the guava (Psidium guajava Linn.), jaboticaba (Myrciaria jaboticaba (Vell.) Berg.), and mango trees (Mangifera indica Linn.) were chosen for observations of Anastrepha. We offered live Anastrepha larvae on soil beneath the tree crowns. We observed for 10 min whether ants removed the larvae or the larvae buried themselves. Eight ant species were responsible for removing 1/4 of the larvae offered. The Pheidole Westwood, 1839 ants were the most efficient genus, removing 93% of the larvae. In compacted and dry soils, the rate of predation by ants was greater. Therefore, this study showed that ants, along with specific soil characteristics, may be important regulators of fruit fly populations and contribute to natural pest control in orchards.

Nest structure and occurrence of three species of Azteca (Hymenoptera, Formicidae) in Cecropia pachystachya (Urticaceae) in non-floodable and floodable pantanal areas

Thirty Cecropia pachystachya trees were examined in non-floodable and floodable areas to investigate the association between C. pachystachya and Azteca ants in the Pantanal of Mato Grosso do Sul, Brazil. The species Azteca ovaticeps, Azteca isthmica, and Azteca alfari were found nesting inside domatia of C. pachystachya. A. ovaticeps was the most frequent species in the trees in the floodable area, while A. isthmica and A. alfari, in the non-floodable area. A. ovaticeps and A. isthmica maintained more entrance/exit holes in comparison to A. alfari. All Azteca species maintained entrance/exit holes in the closest domatia to the apical area of the branch, due to proximity to Mullerian and pearl bodies, suggesting that these species of Azteca were influenced by their environment during evolution and became specialized. All internodal septa of each examined branch were perforated by ants, indicating the branches were inhabited by a single colony.