Olfactory learning, its development and changing role in Honeybee (Apis Mellifera) behaviour

The honeybee (Apis mellifera) is capable of showing a wide variety of cognitive tasks,\nand can be readily conditioned in the laboratory to specific odours, paired with a sucrose\nreward, using the proboscis extension reflex (PER) learning paradigm. This thesis aims\nto establish any differences in the behavioural parameters of this olfactory learning.\nA strong, repeatable methodology is developed, and this specificity of the learning,\ntested by training bees to different odours, provides a useful model of other\nphenomenon important in learning theory, such as overshadowing, blocking, massed\nand spaced training effects, and habituation. The research also indicates a circadian\nrhythm in the olfactory learning, which is linked to the field, where food sources are\nonly available during certain periods of the day.\nA new technique was developed to investigate long term captivity and the effects this\nhas on olfactory learning and homing abilities. In both these different, but crucial,\nlearning criteria, captivity played no significant effect, suggesting that the long term\nmemory of the honeybee is a stable, and not easily disrupted entity.\nThe behavioural and developmental stages of the dynamic honeybee colony were\nexamined, to identify any differences in learning in bees aged 1-24 days old. Bees\nyounger than 15 days of age did not show comparable learning to adult foragers, despite\nhaving a fully mature olfactory neural pathway.\nSimilarly, PER learning of different castes was researched, with nurse, guard, forager,\nand precocial forager bees being studied. The results showed that there exists a heirachy\nin olfactory learning with nurse and guard bees exhibiting learning lower than foragers\nand precocious foragers. This suggests the social role of the bee, and the interaction\nbetween behavioural maturation within its complex society, is a major determinant of\nolfactory learning ability.\nThe effects of the season are also examined to see if the levels oflearning are constant\nover the year. Learning was reduced in the summer months, with an increased learning\nin the winter, which is related to the available forage and the hive demography.\nThe experiments reported show that by using just one example of bee learning, insights\ninto the mechanisms oflearning and memory can be sought. The olfactory system of the\nhoney bee is particularly well researched, and thus, bees can be easily used as a tool at\nall levels of enquiry from molecular and cellular studies to behavioural genetics,\nanatomy and physiology.