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