Optimizing Supplementary Pollen Mixtures For Bumblebee Bombus Terrestris Colonies Based On Colony Reproductive Variables

Pollen is the most important food resource for colony development of bumblebee. Different pollen mixtures show various influences during the artificial rearing involved a number of developmental traits. To select representative traits is the precondition of accurately evaluate the nutritional value of pollen. The purpose of this study is to clarify the representative developmental traits and optimize the feeding pollen mixtures according to these traits. The results of this study were as follows:(1)Assessing on colony developmental traits of the bumblebee Bombus terrestris. In this study we used B. terrestris and three pollens include apricot(Armeniaca sibirica), willow(Salix caprea), and oilseed rape(Brassica rapa).These pollens were mixed according to {3,3} mixture design to get seven pollen mixtures. Eleven traits including egg laying delay, larval ejection, total number of larvae, total weight of larvae, total number of pupa, total weight of pupa, duration of drone, total number and birth weight of drone, sperm number and viability of the queenless micro-colony of Bombus terrestris(L.) were measured and analyzed under the seven different pollen mixtures. Variation analysis, correlation analysis and principal component analysis were used to assess the eleven traits. The results showed variations between eleven traits as the average variation coefficient was 46.62%.T test of Pearson correlation coefficient found significant negative correlation between egg laying delay and total number and weight of pupa, significant positive correlation between total number of pupa and total weight of pupa, also between total weight of larvae and total number of drone. The eleven traits can be summarized as larval development factor, pupa development factor, drone development factor and developmental cycle factor(including egg laying delay, total number of larvae, total weight of pupa, total number of drone, sperm number and sperm viability) to evaluate the micro-colony development of B. terrestris according to the principal component analysis.(2) Optimizaton of the feeding pollen mixtures of the bumblebee Bombus terrestris. Based on the six representative traits, 6 regression models were gained. Results showed all regression models were significant(P < 0.01), but the regression model of sperm number was rejected as its lack of fit showed significant(P < 0.01). Optimized pollen mixtures of the rest five regression models are : only oilseed rape pollen for the shortest egg laying delay, the biggest total number of larvae, the largest total weight of pupa; willow : oilseed rape = 1:1 for the largest total number of drone and sperm viability.The results show the representative colony developmental traits of B. terrestris micro-colony and optimize the feeding pollen mixtures. This study is useful for further research on nutritional requirements of different phase of commercial bumblebee colony development.