Research relating to the honey bee is inevitably a multi-faceted affair. Its eusocial nature, domestication by man and value in providing crucial ecosystem services are all topics worthy of investigation. The colony losses reported worldwide in the last decade served as a catalyst for more research to be aimed at elucidating some of the mysteries surrounding this most studied of insects. As the results of numerous investigations trickled in, scientists around the world started to get a sense of the various threats faced by honey bees while at the same time becoming more aware of the role humans played in their decline. Pathogens and parasites including bacteria, fungi, viruses, mites and insects have now been mostly described. More recently the effects of pesticides, land use changes and numerous interactions are unfolding to create a more complete picture. This dissertation is the combination of experimental and descriptive work at the colony, smaller social group and individual levels as well as in a greater pollinator context. Its aim is to confirm and deepen our understanding of the biology and life-history of the Western honey bee, Apis mellifera.

In an ever-changing landscape of flower patches and increase in intensive agricultural practices, the forage availability around a honey bee colony can have a strong impact on its success. In the first part of the thesis, I focus on investigating whether the immediate type of landscape around a colony is a determining factor in the productivity of that colony. Using long term data based on the daily weight of colonies spread around Denmark, we showed that colonies in urban landscapes, surrounded by parks and private gardens are more productive than their counterparts in agricultural landscapes, surrounded by large monocultures and virtual foraging deserts for much of the year.

The successful running of the colony is also affected by the numerous pests mentioned above. Part two of the thesis deals with what effects a microsporidian gut parasite, Nosema ceranae can have on the behaviour of groups of honey bees exposed from early-on in their adult life. The creation of a laboratory assay enabled us to focus on a wide range of behaviours, some individual, some social, and on the relationship to a make-shift queen. We found that highly parasitized bees had increased rates of trophallaxis, increased walking rates and that their attraction to a queen mandibular pheromone decreased compared to control and lesser-parasitized bees. As a continuation, the third part of the thesis deals with the mechanisms by which parasitized bees are able to limit their transmission potential to a queen. An assay was created to investigate if individual bees vary their rates of interaction with a queen bee, based on their health status. Some of the methodological novelty, set-backs and preliminary results are discussed. In the fourth part, the thesis concludes by zooming out of the confines of the inner hive in order to address recent concerns regarding the potential spill-over of honey bee pathogens to other pollinators.

The threat of inter-specific pathogen transmission appears to be real, and testing the infectivity of honey bee pathogens on other bee pollinators, represents a logical step following on from the recent detection of those pathogens using molecular methods. The preliminary results of a bioassay reveal Osmia rufa bees exposed to N. ceranae spores did not appear to have a reduced lifespan, and N. ceranae infections did not develop as observed in honey bees, the primary host. Further analysis of the ongoing experiment will consolidate the results and allow for the inception of a valuable discussion about the adoption of new environmental and ecological policies.