Pathogens and parasites are rarely ubiquitous within any population. Consequently, when an individual or only a few individuals of an invasive species are moved to a new environment they experience a bottleneck that could potentially limit the probability that pathogens or parasites are also moved to the new range. The invasive species may thus be ��released�� from biotic interactions that can be a major source of density-dependent mortality. A recent review found similar numbers of studies supporting as questioning the hypothesis. This review did find significant evidence to support aspects of the enemy release hypothesis including that invasive species experience less infestation with enemies in their exotic compared to native range. The common wasp ) is an invasive species native to and widespread in Eurasia. In New Zealand these wasps can reach the world��s highest known densities of up to 370 wasps per m2 of tree trunk and 34 nests per ha. These high densities are the driver of substantial ecological impacts, which include high predation rates on invertebrates and the domination of food resources. Populations of these wasps in Argentina and New Zealand appear to have originated in Western Europe, with populations in the invaded range exhibiting high genetic similarity to those from Belgium and the United Kingdom. Densities of common wasps within the native range fluctuate substantially. Years of high abundance are frequently followed by years of scarcity, with queen productivity varying by a factor of 100 between different nests and years. These results suggest some form of endogenous density- dependence, which in addition to exogenous factors such as climate can promote high wasp abundances. Population dynamics within the introduced range show much less fluctuation. This Doxorubicin difference in abundance and population fluctuation might be related to several factors including food availability and the abundance of natural enemies such as pathogens and parasites. The diversity and potential regulatory role of pathogens and parasites in social insects has been highlighted by “colony collapse disorder” in honey bee populations. The exact causes of this disorder in honey bees are unknown, but likely involve a combination of several pathogens or parasites. In addition, the PR-171 beneficial gut bacterial communities of bees are gaining increasing attention as likely mediators of pathogen effects. Pathogens and mutualistic microbes alike may be transferred horizontally, even between species, by behaviours such as feeding on the same food source and hive robbing. Rose et al. found records of 50 fungal, 12 bacterial, five to seven nematodes, four protozoans, and two viral species from wasps in the genera Vespula, Vespa, and Dolichovespula. More recent work has reported additional pathogens and parasites in Vespulid wasps.