Analysis of Mortality in Africanized Honey Bee Colonies with High Levels of Infestation by Varroa destructor

The mite Varroa destructor (Anderson & Treuman 2000) is one of the world's most important plagues of apiculture. In Brazil this mite does not encounter good conditions for parasitism because weather conditions are not ideal for its maintenance, and some strains of Africanized honey bees are resistant to the parasite. This status is reflected in the low number of dead colonies caused by varroatosis and also the stability of infestation levels. The aim of this study was to evaluate the damage caused by mite infestations in hives with higher levels of infestation than the ones considered normal for Brazilian apiaries. The level of infestation in each colony was determined and the mortality rates of parasitized bees during development were periodically recorded. The G Test of Independence and a Test of Proportions were used to compare the data. The rates of mortality of pupae and larvae were mostly proportional to the level of infestation in each colony. All colonies showed mortality rates significantly higher than the control one. In Africanized honeybee colonies with high rates of infestation by Varroa destructor mortality rates varied from 19.27% to 23.28% in pupae ((X) over bar = 21.27%) and from 15.71% to 16.15% in larvae ((X) over bar = 15.93%), against 3.85% and 3.74% in the control colony, respectively. In the parasitized colonies the average rates of mortality caused by the hurtful effects of the mite were, respectively, 5.52 and 4.26 times greater in those two developmental stages. Thus it can be concluded that even in tropical regions, like Brazil, it is necessary to give special attention to the levels of mite infestation (IR), particularly where the IR tends to be higher.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Effects of Natural Infestations of the Mite Varroa destructor on the Development of Africanized Honeybee Workers (Apis mellifera)

The mite Varroa destructor (Anderson & Treuman 2000) has caused extensive damage to beekeeping worldwide. In Brazil, weather conditions and the strains of bees do not provide ideal conditions for mite parasitism, which is reflected in the low number of deaths of colonies caused by varroatosis well as the stability of infestation levels. The aim of this study was to evaluate the damage caused by the mite infestation in hives maintained in natural conditions. For this purpose the number of mites per bee was calculated and used to quantify the level of infestation in each colony. To record the mortality rates of parasitized bees during development daily checks were performed. The data were analyzed by G test of independence and a Test of Proportions. The results indicate that the rate of mortality of pupae and larvae was proportional to the degree of infestation in each colony, and all colonies showed mortality rates significantly higher than the control rate. A significant interaction among death rates recorded between the third and fourth days of larval life and the total death of larvae was found (G Test = 50.22; P = 8.78%) and from 6.13 to 13.48% in larvae ((x) over bar = 9.91%), against 3.85% and 3.74% in the control colony, respectively. Therefore, in the infested colonies the average rates of mortality caused by the harmful effects of the mite were, respectively, 2.28 times and 2.65 times greater in those two developmental stages

Influence of Abiotic Factors and Floral Resource Availability on Daily Foraging Activity of Bees

In this study, the daily and seasonal influences of abiotic factors and the amount of floral resources on the foraging frequency of bees were determined. The experiments were performed, during 12 consecutive months, in the main floral sources used by bees in a secondary forest fragment. The foraging frequency of each bee species on flowers of each plant was recorded for 20-min periods, every hour. To verify whether the foraging activity is influenced by abiotic factors, Pearson's correlation analysis and linear regression tests were performed for the dominant bee species. Temperature and luminosity were the two main abiotic factors regulating foraging activities of bees. A positive correlation was found between the foraging frequency of most bees and these two variables. Conversely, the foraging activity was influenced neither by the relative humidity nor by the wind speed. The activity of each species depends on a combination of factors that include not only abiotic variables, but also the amount of floral resources available during the day, body size, and behavior of each visitor. After a certain period of the day, the scarcity of floral resources produced by most plants can stimulate the bees to forage in the flowers early in subsequent days, which may occur before the period in which the abiotic conditions are really favorable

Effect of paprika on the ovarian development of Africanized honeybee workers (Apis mellifera L.) in queenless colonies

This paper deals with the influence of paprika in the ovarian development of Africanized honeybee workers in recently orphaned colonies. A beehive, whose queen had been naturally mated, was divided into two orphan nuclei. One was fed with candy once a week. The other nucleus received candy (47.5g) plus paprika (2.5g). Newly-emerged workers of both colonies were marked with paint and later collected and dissected at 15, 20, 25, 30, 35, 40 and 45 days of age, in order to compare the ovarian development. A considerable difference between the two groups of bees in relation to the frequency of workers with inactive and active ovaries was observed. A precocious ovarian development was detected in 15-day-old workers who received paprika. This result could be explained by the fact that paprika presents a great concentration of bixin, a carotene that is rich in vitamin A.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Exploitation of floral resources on Sparattosperma leucanthum (Bignoniaceae): foraging activity of the pollinators and the nectar and pollen thieves

The interaction between floral visitors and plants in natural ecosystems has become a major subject in studies on biodiversity conservation. However, there is a very complex interaction between the community of floral visitors and the plant species foraged by them in the natural environment and little is known about the foraging activity of these visitors. Thus, the objective of this study was to determine the composition of the community of floral visitors to Sparattosperma leucanthum in an area under natural regeneration, focusing on the assessment of the exploitation of floral resources by the predominant visitors and effective pollinators. To accomplish this objective, we recorded the activity and behavior of the floral visitors throughout the day in a 2- to 3-m(2) area of flowering branches of S. leucanthum. The model established in the current study comprises the occurrence of a high number of species with few individuals, whereas few species are represented by many individuals. The five predominant species were Apis mellifera, Trigona spinipes, Bombus sp1, Hylocharis chrysura, and Halictidae type 1. of these species, only Bombus sp1 seemed to effectively pollinate the flowers.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

The Effects of Nectar-Robbing on Fruit Production in Sparattosperma leucanthum (Bignoniaceae)

Many animals behave as robbers or thieves of floral resources, causing damage to floral tissues or consuming resources used to attract pollinators, or producing effects similar to emasculation by reducing the pollen load in the anthers (which generally results in losses in terms of sexual reproduction). The present work examined the direct and indirect impacts caused by nectar-robbing on the reproductive success of Sparattosperma leucanthum. Different manipulations of the flowers were tested to determine if fruit production was influenced by the perforations made in the floral tissues (direct damage), and if there were changes in visitation frequencies or in the behaviors of effective pollinators (indirect damage). Perforations made by nectar robbers did not lower the reproductive success of the plant species studied. The bee Trigona spinipes was the most frequent visitor and caused the largest perforations in the calyx and corolla of S. leucanthum. Additionally, we noted the occurrence of pollen theft by this same bee in flowers that had been protected against nectar-robbing. These results suggest that if S. leucanthum had developed a mechanism of resistance to robbery by T spinipes it would probably have experienced even lower pollination levels as a result of reductions in the quantities of pollen available for transfer by effective pollinators. We were not able to evaluate if nectar depletion through robbery modified the behavior of the effective pollinators (bumblebees of the genus Bombus)

Influence of Prey Size on the Capture of Social Wasps (Hymenoptera: Vespidae) by the Orb-Web Spider Nephilengys cruentata

The objective of the present study was to evaluate the plasticity of the hunting behavior of the spider Nephilengys cruentata (Araneae: Nephilidae) facing different species of social wasps. Considering that wasps can consume various species of spiders and that their poison can be used as defense against many predators, the effect of the corporal size of the prey was evaluated in the behavior of N. cruentata. Predation experiments were conducted using three species of social wasps of different sizes and the data registered in this research were compiled through annotations and filming of the hunting behavior of each spider, in relation to the offered prey. The results revealed that the size of the wasp and the sequential offer of prey change the hunting behavior of the spider, and prey of large size have high influence on this behavior.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq