3.2.1.3. Investigating behavioural interactions of adult honey bees and adult SHBs at the colony entrance – two alternative options

Option 1 – at the entrance:

Two methods have been developed to investigate adult bee and SHB (or other nest invader) interactions at the hive entrance (Halcroft et al., 2011; Atkinson and Ellis, 2011a):

  1. Build a modified observation hive to facilitate nest entrance observation.
    The entrance corridor to the hives should contain a test arena (Atkinson and Ellis, 2011a, used a test arena of 10 x 20 cm, L x W), with a floor marked with a 1 cm2 grid system (Fig. 13 and 14).
  2. Build a closable partition at both ends of the test arena using acrylic glass or another material.
    Pierce the acrylic glass with holes to accommodate normal airflow into and out of the hive.
  3. Build a side entrance to the test arena through which beetles can be introduced (Fig. 13 and 14).
  4. Conduct the trials under red light conditions to take into account usual SHB flight activity after dusk (Neumann et al., 2012).
  5. Close both doors to the test arena to “trap” guard bees in place in the nest entrance. The doors should be closed slowly and with minimum disturbance in order to not excite the guard bees.
  6. Introduce, for each trial, one adult SHB through the side entrance of the test arena.
  7. Insert likewise a glass bead into the test arena as a control.
    The bead should be roughly the same size and colour as the invader. Atkinson and Ellis (2011a) tethered a 60 mg black bead to a 15 cm piece of monofilament fishing line so that the bead could be retracted from the test arena after the observation period.
  8. Once introduced, record the responses of guard bees to the beetle or glass bead for any length of time though Atkinson and Ellis (2011a) recorded responses for 60 s.
  9. Three potential guard bee responses can be recognized (perhaps more can be discovered using this method):
    Ignore (a bee’s head comes within 5 mm of the subject but without making contact),
    Contact/ interacting (the bee physically contacts the subject in a non-defensive manner, which involves licking of the beetle and antennating), and
    Defend (the bee attempts to sting and/or remove the subject from the nest, Elzen et al., 2001, see section 3.2.1.2. on behaviour)
    In the event that the test arena is not sealed well enough to prevent beetle escape, only trials in which the beetles remain in the arena for ≥30 s should be counted.
  10. After the observation period, open the acrylic glass doors on either side of the test arenas for >10 s to allow movement of honey bees into/out of the central nest area and to reduce guard bee agitation.
  11. Allow time between trials for the beetles to naturally exit the test arena or for the bead to be withdrawn. In Atkinson and Ellis (2011a), the average time between trials was >1 min.
  12. Use test beetles and beads only once.
  13. It is common to trap different numbers of guard bees in the test arena for each trial and colony when following this method. Consequently, convert bee responses to beetles or beads to proportional data to facilitate fair data comparison across trials. Atkinson and Ellis (2011a) state that this is not the proportion of bees performing a given response but rather the proportion of all responses that were Ignore, Contact, and Defend responses. This way, a single bee may demonstrate these behaviours multiple times throughout the observation period and the behaviours be counted.
  14. Analyse data as outlined in the statistical guidelines of the BEEBOOK (Pirk et al., 2013).

Note: Trials should be conducted using multiple observation hives and simultaneously if resources permit. The latter allows one to minimize observation period and weather impacts on behaviour at the nest entrance.

Option 2: T-shaped arena entrances in an observation hive

This option was developed in the Social Insect Research Group at the University of Pretoria (Strauss, 2009). The advantage is that it does not interfere with the ongoing foraging activity of the colony and utilizes the observation, that any given natural colony often has more than one entrance. It further allows the manipulation of the intruder, in this case SHB, without having the risks of releasing guard bees. The T-shaped form (Fig. 13) offers two chambers to introduce intruders from more than one position and prevents any line of sight between the guards and the intruder before the experiments starts.

  1. Attach the T-shape container to the hive.
  2. Give at least three days for the guard bees to recognize the additional hive entrance.
  3. Cover the arena with a glass lid to allow for observations and to prevent SHBs and honey bees from escaping.
  4. Superimpose a grid on the glass if spatial information has to be recorded (see section 3.2.1.1.).
  5. Insert a piece of metal mesh (± 9.5 x 4.9 cm) into the wooden box as a barrier to separate the intruder/SHB and honey bees. Instead of wood also polycarbonate could be used (Köhler et al., 2013). Holes in the mesh are only large enough for SHB to move through, thereby preventing honey bees from moving into the part of the container where the SHB were released. In this design, SHBs have access to both the hive and container whereas honey bees only have access to the hive and the part of the container closest to the hive entrance.
  6. To optimize the observations and to reduce the influence of the observer, record the interactions using a remotely controlled CCTV system.

The recorded footage can be analysed using software designed for behavioural studies.

Advantage of option 2 is that the setup is not interfering with the gas exchange of the colony, normal activity is unaffected, and therefore observations during the day are possible. In addition, ample of space for the observer or additional equipment is available, so one does not have to squeeze between the exit hole and the observation hive.

Note: Depending on the questions asked both options have their advantages or disadvantages. If one needs constant flow of foragers coming into contact with the SHB option 1 might be better. If the experiment should not interfere with the normal activities of the colony option 2 might be more suitable.


Fig. 13. Observation hive with t-shaped container as a testing area attached to it. Figure with permission from the author. DDrawing: Ursula Strauss.

12106VD revised Fig13


Fig. 14. Diagram of the modified observation hive used by Atkinson and Ellis (2011a, b). A. shows a side view of the observation hive. The white arrow indicates the location where beetles are introduced into the observation hive, while the black arrows indicate the location of the eight grooves (confinement sites) located on the periphery of the observation hive. The confinement sites are present on both sides, totalling 16 sites. Invading beetles are more likely to be confined in these sites (facilitating their observation) than in other locations in the nest. B. shows the bottom board of the observation hive (top picture) and a top view of the gridded base (test arena) of the observation hive. The white arrow indicates the location where beetles or control beads can be introduced into the test arena. The black arrows indicate the location of the acrylic glass doors that, when slid in place, capture guard bees in the test arena.

12106VD revised Fig14a

 

12106VD revised Fig14b