Recapping and mite non-reproduction in the endemic honey bee subspecies of Malta : Apis mellifera ruttneri

Abstract

Scientific literature concerning Apis mellifera ruttneri, the endemic honey bee of the Maltese Islands is still limited. Recently, its behaviour and development gained an increasing attention particularly in relation to Varroa resistant traits. Nevertheless, the effect of recapping on mite reproduction remains controversial. In October 2021, a standardized study was set up for the evaluation of two resistant traits: recapping and mite non-reproduction (MNR). In total 40 colonies (A.m.ruttneri n = 20, and Buckfast n = 20, sister queens) of approximately the same size, were distributed across two apiaries, one in Wardija and the other in . Hygienic behaviour evaluated by the pin-test method was higher in the Buckfast than in A.m.ruttneri, but this was not significant. In contrast, A.m.ruttneri produced significantly more honey than the Buckfast group. MNR is very restricted for analysis due its strict requirements in the right number of mites in relation to the brood. A Varroa treatment in December 2021 was applied to reduce mite loads, subsequently the first MNR/recapping assessment occurred in June 2022 and continued until April 2023. The measurements were repeated three times across a ten-month period, but samples could not be further collected due to insufficient mite infestation and colony losses emerging from to constant strain of the mites. High recapping rates and low mite reproductive success were consistent in A.m.ruttneri. In the Buckfast group, both at the colony level and at the cell level elevated rates of recapping were linked with MNR. However, this direct outcome of recapping on mite reproduction was not observed in A.m.ruttneri. Even though, both traits seem to mainly be driven by seasonality and apiary environment, this effect was stronger in A.m.ruttneri. Brood infestation related to an increased non-targeted recapping in A.m.ruttneri but not in the Buckfast. Despite brood infestation was relatively high, most colonies preceded by A.m.ruttneri still survived until the end of the study, and afterwards. All this implies that A.m.ruttneri shows a certain degree of tolerance and resistance expressed both through MNR and an extensive mite infestation tolerance. This is likely due to a combination of recapping and possibly other traits such as VSH, physiological adaptations along with the rhythm of brood dynamics amalgamated to the seasonal changes of to the Maltese Islands.