Varroa mite


nutrients and blood cells contained in the haemolymph (Martin et al., 1998; Bowen-Walker et al., 1999; Ongus et al., 2004). Infested colonies eventually die out unless control measures, such us Oxalic acid treatments, are applied in a timely fashion (Morton et al., 2005).

V. destructor completes its entire lifecycle within the hive. This comprises a stage as an adult parasite living on adult bees (phoretic stage) and a reproductive stage inside the sealed brood cells (Morton et al., 2005).

To breed, an adult gravid female mite enters occupied brood cells just before the cell is capped with wax by adult honey bees. Mites prefer to breed in drone brood, but will also breed in worker brood (Morton et al., 2005). About four hours after capping, the female starts feeding on the immature bee and establishes a feeding site (open lesion) on the developing bee that her offspring can feed from as they develop. About 60-70 hours after capping the female lays the first of her eggs; each female lays 5-6 eggs. Mating between male and female mite offspring occurs within the cell (Morton et al., 2005).  The mite offspring develop through two juvenile stages known as the protonymph and deutonymph before becoming adults. Mature female mites leave the cell when the host bee emerges. Some of these may produce a second or third generation of mites by entering new brood cells.

Mite population growth is influenced by the development and status of a colony, and depending on circumstances mite numbers will increase between 12 and 800 fold  (Morton et al., 2005). Such an ability to multiply means that Varroa is The number one problem in beekeeping. Beekeepers can treat the hives with natural and chemical treatments, but Varroa has shown an extraordinary tolerance and resistance to both (Milani et al., 1999; Lodesani et al., 1995).

It is possible to find detailed information about Varroa in Fera - National Bee Unit website (follow Useful links page) where is also possible to download the leaflet Managing Varroa.

Varroa destructor (Acari: Mesostigmata: Varroidae) (Figure 1) is an external parasite of honey bees. Varroa dimensions are: (L) 1.1 mm X (W) 1.6 mm for the female and (L) 0.8 mm X (W) 0.7 mm for the male. The colour of the female is reddish brown, the male is greenish-white; they are crab-shaped (Morton et al., 2005).

Originally confined to Apis cerana it has spread in recent decades to Apis mellifera because of the introduction of this species in Asia due to its high honey production (Morton et al., 2005).

The mites feed on both adult honey bees and brood, weakening them and increasing the spread of honey bee viruses by the use of penetrating mouth-parts. In fact it is recognised that Varroa can be an active vector (the virus can replicate in it) of some honey bee viruses (such as DWV) so the parasite can increase virus titre and can efficiently transmit by injecting the viruses directly in the haemolymph, overcoming the mechanical defences of the bee and the immune defences by depleting the bee of

Varroa destructor, an important vector of viral diseases

FIG 1: Adult female varroa mites (red arrows) on a worker bee. Varroa mites usually bite in positions where the honey bees cannot groom properly  (Crown copyright, National Bee Unit, FERA)