Submitted to: Journal of Apicultural Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/1/2008
Publication Date: 9/1/2008
Citation: De Guzman, L.I., Frake, A.M., Rinderer, T.E. 2008. Detection and removal of brood infested with eggs and larvae of small hive beetles (Aethina tumida Murray) by Russian and Italian honey bees. Journal of Apicultural Research and Bee World 47(3):216-221. Interpretive Summary: Hygienic behavior is an important part of honey bees’ defense to diseases, pests and parasites. In the African honey bees, which are known to be resistant to small hive beetles (SHB), removal behavior toward different stages of SHB is well-developed. Removal of adult SHB and brood infested with SHB eggs was also observed in European honey bee (EHB) colonies but at a lower degree. Nevertheless, the removal of SHB egg-infested brood by different stocks of EHB has not been studied. In this study, we compared the response of Russian and Italian honey bees toward SHB-infested brood. We observed that both honey bee stocks were able to detect eggs inside the sealed brood. Within 6 h, both stocks emptied about 40-50% of the brood with perforations of the cell wall (NCYW) and both of the capping and cell wall (YCYW). This early defensive response against eggs of SHB is advantageous in preventing further damage to honey bee colonies by larval feeding. After 20 h, the cumulative removal rates of 85.11 ± 2.98% (Italian bees) and 84.32 ± 4.29% (Russian bees) were observed. Our results show that both Italian and Russian honey bees can detect, uncap and remove brood infested with eggs and larvae of SHB. This removal of brood with eggs and larvae contributes to the overall defense of honey bees against SHB.
Technical Abstract: The response of Russian and Italian honey bees to brood infested with small hive beetle (SHB) eggs and larvae was compared. Test brood was grouped as follows: a) NCNW = no perforation either of capping or cell wall; b) NCYW = perforation of cell wall only; c) YCNW = perforation of capping only; and d) YCYW = capping and cell wall perforations. All perforations were made by SHB. Our results showed that brood cells with perforations of the cell wall (NCYW and YCYW) had the highest infestation (76.53 ± 2.10%) and intensity of eggs (58.46 ± 2.85 eggs). YCNW only showed low levels of infestation (29.17 ± 3.31% and 15.60 ± 1.31 eggs per infested cell). Hence, we calculated brood removal based on data from NCYW and YCYW groups. We observed that both honey bee stocks were able to detect eggs inside the sealed brood and remove them with the infested brood. Within 6 h, both stocks removed the contents of 39.24 ± 4.94% of the cells in the NCYW group. A higher removal rate of 50.51 ± 5.80% was observed when brood had perforations both of the capping and cell wall (YCYW). These two groups of brood had the highest numbers of eggs per infested cell (50-70 eggs). Thus, the removal of about 40-50% of brood infested with eggs within 6 h was an early defensive response against SHB. Eggs hatched after the 6 h observation and subsequent hygienic removal was of brood infested with larvae. At 20 h, additional 56.41 ± 4.62% (NCYW) and 42.04 ± 4.91% (YCYW) removal rates were observed. Overall, the cumulative removal rates for both stocks were similar with means of 85.11 ± 2.98% and 84.32 ± 4.29% for the Italian and Russian honey bees, respectively. The detection of eggs inside the brood cells during the first 6 h was probably enhanced primarily by olfactory cues. It is possible that SHB egg deposition induces the production of volatiles. Detection of brood infested with SHB larvae was probably facilitated by the release of honey bee volatiles in response to SHB larval feeding. In addition, feces of SHB larvae may have assisted worker bees in locating infested cells. Our results suggest that both stocks have good olfactory sensitivity and hygienic responses to both SHB eggs and larvae. Removal of brood with eggs and larvae contributes to the overall defense of honey bees against SHB.