Proboscis conditioning experiments with honeybees, Apis mellifera caucasica, with butyric acid and DEET mixture as conditioned and unconditioned stimuli

Abstract

Three experiments are described investigating whether olfactory repellents DEET and butyric acid can support the classical conditioning of proboscis extension in the honeybee, Apis mellifera caucasica (Hymenoptera: Apidae). In the first experiment DEET and butyric acid readily led to standard acquisition and extinction effects, which are comparable to the use of cinnamon as a conditioned stimulus. These results demonstrate that the odor of DEET or butyric acid is not intrinsically repellent to honey bees. In a second experiment, with DEET and butyric acid mixed with sucrose as an unconditioned stimulus, proboscis conditioning was not established. After several trials, few animals responded to the unconditioned stimulus. These results demonstrate that these chemicals are gustatory repellents when in direct contact. In the last experiment a conditioned suppression paradigm was used. Exposing animals to butyric acid or DEET when the proboscis was extended by direct sucrose stimulation or by learning revealed that retraction of the proboscis was similar to another novel odor, lavender, and in all cases greatest when the animal was not permitted to feed. These results again demonstrate that DEET or butyric acid are not olfactory repellents, and in addition, conditioned suppression is influenced by feeding state of the bee.

Figure 1.

Performance of paired and unpaired Apis melllifera caucasica given a conditioned stimulus of either cinnamon, DEET, or butyric acid. The transition from acquisition to extinction occurs on trial 13. Results are reported as the proportion of elicited responses for each trial. High quality figures are available online.

Figure 2.

Comparison of unconditioned responses of Apis melllifera caucasica to sucrose alone, sucrose mixed with DEET, or sucrose mixed with butyric acid in animals receiving paired or unpaired training. Results are reported as the proportion of elicited responses for each trial. High quality figures are available online.

Figure 3.

Effect of butyric acid (BA), DEET (25%), and lavender odor (control odor) on proboscis extension by Apis melllifera caucasica elicited by antenna stimulation. Results are reported as the proportion of elicited responses. High quality figures are available online.

Figure 4.

Effect of butyric acid (BA), DEET (25%), and lavender (control odor) on proboscis extension elicited by learning in Apis melllifera caucasica. Results are reported as the proportion of elicited responses. High quality figures are available online.