Effects of Larval Age at Grafting and Supplemental Feeding on Morphometrics and Oviposition in Honeybee Queen (Apis mellifera scutellata, Hymenoptera: Apidae) in Karura Forest, Kenya

Abstract

In Africa, honeybees provide critical pollination services, nutrition and income for smallholder farmers. However, because of pests and pathogens honeybees are under threat of population decline. Moreover, lack of adequate research on the existing queen rearing technologies has led to decline in honeybee queen quality. The honeybee queen is the repository of a colony’s heritable genetic traits, its superiority determines the productivity and resilience of the colony. Effects of factors such as age of grafted larva, supplemental feeding and mating are not known for African bee races. To bridge this gap, a study was undertaken at the International Centre of Insects Physiology and Ecology (ICIPE) Karura forest apiaries in Kenya to determine the effect of larval age and supplemental feeding on morphometrics and oviposition in the honeybee queen Apis mellifera scutellata. Queens were reared in 12 colonies with two feeding regimes. Five larval age groups, 6, 12, 24, 36, and 48 hours old were used to raise queens. Specific morphometric parameters of the queens were determined. The wet weight, spermatheca volume and the external parameters (head length and width, wing length and width and thorax length and width) of the emerged queens were recorded. Oviposition rate in Naturally Mated queens (NM) and Artificially Inseminated queens (AI) was determined by recording the number of eggs laid daily. Multivariate Analysis of Variance (MANOVA), Analysis of Variance (ANOVA), and Student-Newman-Keuls (SNK) test were used to evaluate the effect of larval age and supplemental feeding on queen quality. The oviposition rate of naturally mated and artificially inseminated queens was evaluated using t- test. Results showed that age of grafted larvae and supplemental feeding significantly affect the morphometrics of the reared queens (p = 0.001). The 24-hour-old larvae were heavier and larger in most of the external parameters and thus it is the optimal age for grafting in A. m. scutellata queens. Oviposition rate was the same in both the NM and AI queens. Further study is required to establish any correlations between the quality of the queens produced from the different age groups and overall colony productivity.