The effect of age and sexual maturation on thermal preferences of honey bee drones.

The thermal preferences of Apis mellifera carnica drones (male individuals) are poorly understood, though their reproductive quality affects the quality of the inseminated queen and the whole honey bee colony. Therefore, the aim of this study was to determine the thermal preferences of individual drones according to their age and sexual maturity. Drones at the ages of 1, 5, 10, 15, 20 and 25 days were tested. The drones were placed on a platform in a temperature gradient in the range 20 °C and 46 °C. The thermal preferences of the drones were measured with the use of a thermal-imaging camera. Drones significantly differed with their choice of a preferred temperature. The one-day-old and the 25-day-old drones preferred the lowest temperatures. A slightly higher temperature was preferred by the 5-day-old drones, and the highest temperature was chosen by the drones at the ages of 10, 15, and 20 days. The changes in the thermal preferences of drones correspond to physiological changes occurring with age and connected with the rate of sexual maturation.

Usefulness of bee bread and capped brood for the assessment of monocyclic aromatic hydrocarbon levels in the environment.

Monitoring airborne pollutants, like aromatic hydrocarbons, are raising more and more concerns recently. Various sampling techniques and methods are known to collect, measure, and analyse environmental pollution levels based on honey bee bodies or bee product samples. Although honey bees are studied in detail and sampling methods are becoming more and more sophisticated biological samples may significantly differ in pollutant accumulation, showing a wide range of pollution levels even in the same site and environment. We have compared the pollution levels of honey bee capped brood and bee bread (pollen collected by honey bees and deposited in the hive) originating from four sites during two years of study and twelve honey bee families near various pollution sources emitting monocyclic aromatic hydrocarbons (BTEX) to the environment. Our result showed, that the environmental monitoring of BTEX can be based on sampling honey bees, and bee bread in particular. However, we found a significant difference in the uptake of these pollutants regarding sample type. Pollen collected as a food source revealed consistently higher levels of BTEX than bee brood, as well as some other differences in pollution levels between samples and between seasons, as opposed to capped brood. Based on our results, we suggest that for measuring and monitoring of BTEX pollution in the environment the use of bee bread is a valuable source of information.

Honey bees are larger and live longer after developing at low temperature.

Honey bees (Apis mellifera) are known to be temperature specialist and actively maintain brood temperature in a very narrow temperature range. Developing larvae are sensitive to changes of temperature in the nest. Temperatures lower than generally assumed as optimal have been shown to cause a number of negative developmental and behavioural changes in honey bees. We have reared both worker and drone larvae during the capped brood stage in cold (32 °C) and in warm temperatures (35 °C). Next, we measured their body mass at emergence and the longevity of individuals either caged in incubator (workers) or placed in maintaining colonies (drones). For drones, the reproductive caste, we also compared the mass and ratio of body parts (head, thorax, and abdomen) to body mass. As expected, both castes were heavier when reared in cold, but contrary to our expectations, both castes survived longer after emergence than bees reared in warm. Drones reared in cold were characterized by proportionally larger abdomens, in comparison to drones reared in warm.

Influence of carbon dioxide on Nosema apis infection of honeybees (Apis mellifera).

Young workers of the honeybee Apis mellifera carnica were individually inoculated with Nosema apis spores subjected to carbon dioxide (CO(2)) treatment. The spores were kept in a CO(2) atmosphere for 30, 35 and 40 h. The course of the infection was evaluated on the basis of the survival rate of bee workers and the number of N. apis spores in their digestive tracts. CO(2) treatment of N. apis spores resulted in faster proliferation of the parasite as well as higher mortality among workers infected with spores kept in CO(2) for 30 and 35 h.