Studies on the ecology of hive beetles in Kenya

Abstract

Although beekeeping has become an important economic venture in Kenya, and is being used to alleviate poverty and promote environmental conservation, very little information exists on arthropods associated with honey bees in the country. This is especially true for hive beetles which cause great damage to honey bees and hive products. With knowledge on the biology of these beetles and their chemical ecological interaction with honey bees virtually nonexistent, this study was carried out to close this knowledge gap with the goal of providing key data towards further development into potential management tools for these beetles. Nation-wide surveys in Kenya covering major beekeeping areas identified three beetle pests of honey bees viz Aethina tumida Murray, Oplostomus haroldi Witte and Oplostomus sp. Aethina tumida was cosmopolitan whereas 0. haroldi and Oplostomus sp. are confined to the eastern and coastal parts. Beetle infestations differed across sites being higher in areas with high precipitation and those close to water bodies suggesting that climatic factors influence their distribution. Inside the hive, A. tumida occurred mainly on the bottom board and the scarabs on the frames. Adult scarabs caused damage by feeding on bee brood, pollen and honey with a greater preference for the brood. Discrimination of the scarab beetles was shown to be possible using mtCOI gene and DNA barcodes. Oplostomus haroldi was reared successfully on a diet of cow dung mixed with soil and it took 3-5 months to develop from egg to adult implying that these scarab pests can produce more than one generation per year depending on prevailing climatic conditions. Behavioural and electrophysiological assays together with coupled GC-MS analyses showed that both sexes of 0. haroldi were significantly attracted to honey bee volatiles and mainly detected their esters. This may imply that this beetle uses honey bee odours as olfactory cues to locate its hos tAnalysis of the mating behavior of 0. haroldi showed five distinct stages namely, arrestment, alignment, mounting, copulation and post-copulatory mate guarding. Males distinguished other males from females using their maxillary palp tips and, a female contact sex pheromone composed of hydrocarbons. Of these hydrocarbons, (Z)-9-pentacosene, the dominant female component, elicited a partial mating behavior confirming its pheromonal role. Behavioural assays also showed that volatiles from Mangifera indica L. and Musa acuminata x Musa balbisiana Colla significantly attracted both male and female beetles. In electrophysiological assays, components of the volatiles from both fruits were electrophysiologically active with components from M. indica being 2-3 times more active compared to M. sapientum. Coupled GC-MS analyses showed that the bio-active peaks were mostly terpenes, esters and ketones, with a number of them known to be produced by honey bees. Field trapping using A. tumida flight traps baited with ripe mango and banana fruits confirmed laboratory results which show that this beetle is attracted to ripe fruits in nature and can reproduce on them. Overall, this study has revealed the diversity of beetles associated with honey bees in Kenya and gives a hitherto unknown account of the life history of the scarabs under laboratory conditions. It also demonstrates the use of olfactory and contact cues by 0. haroldi for host location and mating, respectively. The possible use of alternate hosts by A. tumida is also demonstrated.