3.4.3. Marking mites
Varroa mites can be marked with paint markers, enamel paint for models, correction fluid polyester glitter or fluorescent pigment (Schultz, 1984; Harris, 2001; Kirrane et al., 2012). Methods with paint are faster to use and have been shown safer for the mites. Toxicity is mainly due to the solvents incorporated in the products.
For paint application, soft tools are preferable to toothpick or other hard tools to avoid injuring the mites. A droplet of paint can be placed on a microscope slide and little quantities collected with a very thin paintbrush or a fishing line (Kirrane et al., 2012) for application on the mite. The hair of a paintbrush can be cut off leaving enough hair to obtain the desired size. The right size of the application tool is obtained when the paint dot is visible, but does not impair the behaviour of the mite.
If the mites are used for behavioural observations during the phoretic or reproductive stage, care should be taken to produce a flat paint mark that enables the mites to push herself between the bees' sternites and feed, or to allow the mite’s free movement within the restricted space between pupae and cell walls.
Before use in large scale experiment, a toxicity test should be performed to ensure that the paint chosen is not toxic to the mite: marked and sham-treated mites should be kept in similar conditions and their longevity compared. Marked mites should live as long as unmarked mites. Refer to section 3.2. ‘Rearing mites in the laboratory’ for rearing methods. To minimise the risk of the paint dot coming off the cuticle and thus prevent recognition of the marked mite at the end of the experiment, preliminary tests with different brands should be made to select a long lasting paint.