Parasites

A parasite lives by taking all the needs of its life from another living organism, often becoming highly specialised for this interaction. Where possible, host organisms will avoid, repel or destroy parasites, while the parasites will evolve survival strategies in response to these defence mechanisms. Since the parasite will usually reproduce faster than its host, it is harder for the host to adapt than the parasite.  However, because it is not in the parasite's interest to kill its host, they frequently adapt to minimise damage to their host. There is a wide range of host-parasite interactions some of which cannot be clearly defined as parasitic.

A number of parasites attack adult or larval honey bees, some of which cause serious difficulties for survival of the colony. The most common parasites of honey bees are members of the mite family, but other minor parasites  are found worldwide from other groups including protozoans (such as amoeba) flies, nematodes and beetles.

Acarine mites (often called tracheal mites) infect the trachea (or breathing tubes) of the adult honey bee having serious effects on the individual bees' capacity to breathe and consequently on the whole colony's ability to collect honey, thermoregulate and respire. In susceptible colonies they can cause high mortality rates.

Varroa mites (Varroa destructor and Varroa jacobsonii) are relatively large mites observable with the naked eye. Varroa destructor causes great damage to colonies of Apis mellifera by parasitising both adult and larval stages of the honey bee. It appears to have crossed the species barrier, from the Asian hive bee Apis cerana to the honey bee Apis mellifera which has evolved no defences against this parasite. This has caused devastating losses of Apis mellifera honey bee colonies in many countiries. However there is some evidence that the Africa and Africanised honeybees have some inherent defence against the Varroa mite although the basis of this is not yet clear. The mites are the vector of a range of viruses that are often benign and symptomless until they are combined with a Varroa mite infestation.

Tropilaelaps is another mite with a similar life history to Varroa. Its native hosts are the Asian honey bee species and with the globalisation of beekeeping, there is potential for this mite also to cross the species barrier into Apis mellifera with unknown consequences.