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