14.4. Conditioning free-flying bees in the field
Honey bee foragers can be
conditioned in the field to discriminate between different sensory cues such as
odours, visual cues and tactile patterns. The basic procedures for conditioning
bees are very similar. A crucial part is the right choice of the conditioning
stimulus, because it has to be designed such that it can also be perceived by
the bees, i.e. for visual cues for example one has to take care of the visual angle,
the distance of perception, the wavelength spectrum, the green contrast, etc.
In Fig. 38 we present one example of
how to condition free-flying bees to a visual pattern in the field. In this
example, a dual-choice test is used for quantifying the learning success. The
test apparatus is a white box with three disk holders mounted horizontally to
each other. The centre has an opening for the sucrose reward. The conditioned
and tested visual cues used in this protocol are vertically and horizontally
oriented black stripes on a white background placed onto rectangular discs (for
more details see Fig. 38). The test apparatus and the stimuli used here are
just one example to explain the conditioning procedure. The discs on the
apparatus can be easily exchanged by other cues, such as colours, tactile cues
or specific odours which are applied on filter papers, depending on the
question of the study.
Fig. 38. An example of a visual conditioning and testing protocol for free flying bees in the field. A. Schematic drawing of the test apparatus (80 cm x 40 cm x 40 cm) used for conditioning and dual-choice testing. The front side of the apparatus is used both for conditioning and testing. Three holders for discs are mounted 20 cm next to each other. The visual, olfactory or tactile stimuli can be mounted on the small rectangular discs (7 cm x 6 cm) that fit into the holders. The centre is used for conditioning and has a 1 cm opening. Bees can enter the small hole in the centre and receive the sugar reward. The left and right holders are for presentation of stimuli during the dual choice test. The discs for testing are closed and have no openings. B – D. Pictures of the conditioning procedure for visual discrimination in the field. B. Training to the setup. A droplet of a 50 % sucrose solution is placed inside the opening of the centre. A black disc placed in the central holder is used as a landmark. The bee tested has to collect the reward during 3 visits before the conditioning procedure can begin. One visit is defined as one foraging flight between the hive and the setup. C. Conditioning procedure. The bee is conditioned to a vertical pattern (conditioning stimulus; CS) placed in the centre in 5 learning trials (= 5 visits). D. Dual choice test. A vertical (CS) and a horizontal (alternative) stimulus pattern are presented on the left and right side. The centre is covered with a white disc. The approaches towards the vertical and the horizontal stimuli are registered for 1 min. Afterwards, the side of the tested stimuli is reversed and the choice behaviour is recorded again for 1 min.