achieve "racial purity" in the breeding of their bees, culminating in the publication of their book The Dark European Honeybee. However the process depends on the exact measuring methods employed. Character A. m. mellifera is descended from the 'M' lineage of Apis mellifera, of which all bees to a greater or lesser degree have aggression when compared to the 'C' lineage. A. m. mellifera hybrids have an even greater reputation of aggression amongst beekeepers, which can increase in subsequent generations if left unchecked, although this characteristic can be overcome with continual selective breeding over some generations. They are nervous and aggressive to the extent that routine inspections will take longer, decreasing the enjoyment of managing their colonies. This characteristic is one that has been traditionally associated with A. m. mellifera going back to the now extinct Old British Black bee before the early 1900s: To quote Brother Adam who was the only beekeeper with first hand experience that committed his findings to paper: "The native (Old British Black) bee had undoubtedly many extremely valuable characteristics, but equally so a great many serious defects and drawbacks. She was very bad tempered and very susceptible to brood diseases and would in any case not have been able to produce the crops (of honey) we have secured since her demise". In 2014-2017 a European wide survey was conducted with 621 colonies, which included the various subspecies kept by beekeepers, it found that the A. m. mellifera was the most aggressive, had the highest swarming tendency and the lowest hygienic behaviour - a trait closely linked with Varroa sensitive hygiene. Characteristics higher levels of aggression increased tendency to swarm lower resistance to varroa mites due to poorer hygienic behaviour (VSH) prone to inbreeding due to habit of Apiary Vicinity Mating, resulting in increased aggression susceptibility to acarine mites due to their larger tracheas difficulty entering smaller flowers due to their larger size difficulty collecting nectar from longer flowers due to their shorter tongues poorer pollinators of fruit trees and bushes more prone to Balling the Queen, resulting in her death susceptible to brood diseases susceptible to a greater likelihood of Supersedure than other bees non-prolific, population building up later in year, unable to take full advantage of an early spring nectar flow A. m. mellifera Queens do not hybridize with non-A. m. mellifera Drones Non-hybridization In 2013 research was carried out in Poland which