Effect of Temperature Treatment during Development of Osmia rufa L., on Mortality, Emergence and Longevity of Adults

The red mason bee (Osmia rufa L.) is a univoltine solitary species of the Osmia genus. This bee is reared on a commercial scale and used as a managed alternative pollinator. We intended that the results of our study would improve the management of this bee so as to synchronise their flying period with the blooming of crops. In the spring, we moved newly occupied nests of the red mason bee to a laboratory and placed them in incubators. Immature development was examined at three constant temperatures, 20°C, 25°C, and 30°C. Selected nests were opened to monitor the subsequent developmental stages. The remaining bees were wintered in nests stored at cool temperature (4°C). In April, we removed the insects from the nests and began incubation at 25°C to establish the emergence time of adult individuals. To determine the survival rate of adult bees, we moved the emerged specimens to cages, where they were fed and kept until death. Temperature increase generally reduced immature development time. But this tendency was not observed in the prepupal stage. During ontogeny the highest mortality rate was observed in wintering adult insects at developmental temperatures of 25°C and 30°C. Bees developing at constant temperatures emerged faster during spring incubation in comparison to those developing in natural conditions. Constant developmental temperatures decreased the survival rate of females as post-emergence adult insects. The survival rate of males was lower at the developmental temperature of 30°C

Reproductive potential and nesting effects of Osmia rufa (syn. bicornis) female (Hymenoptera: Megachilidae)

The red mason bee Osmia rufa is a solitary bee belonging to the family Megachilidae, and is prone to nest in aggregations. Each female builds a nest separately in pre-existing cavities such as holes in wood and walls or empty plant stems. This is done by successively setting the cells in a linear series. In this study, we elucidate the nesting behavior and the reproductive potential of a single O. rufa female. The reproductive potential of nesting females was evaluated after the offspring finished development. We observed that an individual female may colonize up to five nest tubes and build 5-34 cells in them (16 on an average). During the nesting time the number of cells decreased with the sequence of nest tubes colonized by one female, which built a maximum of 11 cells in the first occupied nest and 5 cells in the last (fifth nest). Our observations indicated that 40% of nesting females colonized one nest tube as compared to 7% colonizing five nest tubes. Furthermore, in subsequent nest tubes the number of cells with freshly emerged females gradually decreased which was the reverse with males. Thus, the sex ratio (proportion of male and female offspring) may change during the nesting period. The female offspring predominated in the first two nesting tubes, while in the subsequent three tubes male offspring dominated. We also cataloged different causes of reduction in abundance of offspring in O. rufa females such as parasitization or problem associated with moulting

Variations in antioxidant defense during the development of the solitary bee Osmia bicornis

International audienceAn efficient antioxidant system is of particular importance for insects whose high metabolic rates promote increased formation of reactive oxygen species (ROS). The amount of ROS can be additionally increased by environmental factors. This study investigates the ability of red mason bees (Osmia bicornis L.) to inactivate free radicals during insect development. Both male and female bees were studied, from the larval to the active imago stage. The activity of four antioxidant enzymes, superoxide dismutase, catalase, peroxidase and glutathione S-transferase, was measured; and glutathione content and total antioxidant status were determined. The highest values of the examined parameters were found in feeding stages-in larvae and in active imagines of both genders. Significant differences between genders were noted mainly in catalase activity, which was lower in overwintering imagines and active females than in males. Most differences were observed between females and males after emergence