3.3. Collecting mites from bee brood
Phoretic mites that are moving on the surfaces of bee combs are relatively hard to collect with forceps. In these situations it is best to collect them with a fine bristle bush slightly wetted with honey, water or alcohol (not human spittle as it will contaminate the sample with human DNA) or a small mouth aspirator.
When large numbers of mites are required, it is best to collect them from infested capped bee brood cells. This can be done in the field, or if large numbers of colonies needs to be sampled, combs can be collected and sampled later in the comfort of the laboratory. To do this:
- Remove the wax cappings from a large number of bee brood cells on one side of a comb all at once.
- Remove the developing bee brood from these cells.
- Invert the comb over a sheet of white paper and tap it relatively hard on its upper surface to dislodge mites from the cells onto the paper.
- Collect the mite from the paper into small vials
containing 70% ethyl alcohol, using a fine paint brush wetted in honey, alcohol
or water (not human spittle) or with a fine pair of tweezers, as shown for Varroa mites in Dietemann et al., (2013). Tropilaelaps mites (similar to Varroa
mites) will immediately sink to the bottom of a container when immersed in
ethyl alcohol. The white paper onto which mites fall can also be substituted
with brown paper if mite collection is targeted at nymphal stages.
There are benefits in sometimes collecting live mites into hot water before transferring them into alcohol for storage (Section 4.1 below).
Pros: Mites collected into ethyl alcohol can be subsequently tested in the laboratory in a range of different tests, such as morphometric and DNA analyses.
Cons: Mites used in inoculation or behavioural studies cannot be placed into ethyl alcohol after collection. But even then, mites collected by this method are of little use for those types of studies, as the development stage of the collected mites cannot be ascertained with certain. Live mites to be used in those kinds of studies are best collected from very recently capped bee brood cells that contain late larval or prepupal stages. This ensures that the mites collected are mature adults that are at a specific stage of development – that is, at the pre-reproductive stage. These mites can be kept alive until needed by keeping them in a small Petri dish or a glass bottle with late stage bee larvae.