7.2.2. Feeding devices for providing carbohydrates to caged adult workers in the laboratory

Numerous types of devices can be used to provide liquid carbohydrates to caged honey bees. Feeding devices must fulfil the following minimum criteria:

  • Allows workers to drink safely, without drowning.
  • Holds the respective volume securely, minimises evaporation, and prevents leakage; a small piece of paper tissue can be inserted in the feeder over top of the feeding site to prevent leakage.
  • Ensures feeding sites are not easily blocked by crystallisation; size of feeding site hole that is dispensing food, as well as water concentration of carbohydrate, will influence crystallisation. Since no data are currently available on the subject, pre-trials will determine an appropriate size of feeding site.
  • Allows for quick and easy replenishment of the solution, as well as measurement of consumption, that minimises accidental escape of experimental individuals and preferably does not require opening cages.

For workers in frame or hoarding cages (refer to section 5), a simple disposable feeding device can be made using a microcentrifuge tube (<2 ml) with two to three small holes 1-2 mm wide drilled into the bottom or by using a syringe with the needle removed and adaptor cut away to reveal a 2-5 mm wide hole (Fig. 20). Alternatively, a feeding device can be created by drilling a single 2-5 mm wide hole in the base, as well as two 2-5 ml sized holes on the sides ~5 mm from the tip to prevent air bubbles from forming at the bottom; a small piece of tissue paper can be inserted into the tip to prevent leakage. Gravity feeders, created by inverting a jar with a lid containing a single large hole (i.e. 5 mm) screened with multiple layers of cheese cloth or a lid with three to five 1-mm holes without cheese cloth, can also be used; however, one must be careful of leakage and crystallisation. Quantity and size of feeders should be adapted to the number of workers requiring food and to the interval between food replenishment. At least 2 devices should be used to reduce the risk of workers starving if one feeder becomes defective, especially if it leaks. Leaky feeders can result in workers starving or drowning; use of ventilation holes or absorptive material on the bottom of cages can prevent the latter. Workers in isolation cages can be individually fed using a micropipette (section 7.8.2).

Fig. 20. A disposable 5 ml plastic syringe with Luer connection fitting removed to create a 2 mm hole revealing the black plunger.

Figure 20

 Refer to section 7.3.2 for a description of providing solid food to caged workers in the laboratory.