Published online 1 July 1999 | Nature | doi:10.1038/news990701-13


Bad news for bees

British bees are under threat of extinction because of infestation with a parasitic mite, Varroa jacobsonii. A statement issued on 21 June by the British Beekeepers’ Association warns of serious consequences of varroa infestation both for honeybees (Apis mellifera), and, because bees pollinate many plants, for the environment in which they live.

But the interplay between bees and other animals is more complex than this simple us-and-them picture portrays. The nests, hives and bodies of bees harbour a large community of small animals, the most diverse and numerous of which are mites - minute relatives of ticks and spiders.

The habits of many of these creatures are hardly known at all. Some of them, like the varroa mite, are actively harmful, whereas others are likely to be beneficial; and, as S. Koulianos and H. H. Schwarz of the ETH (Technical University) of Zürich, Switzerland show in the June issue of the Journal of Zoology, animals that you would think of as harmful could actually be beneficial to bees.

In their report, Koulianos and Schwarz present a basic study of the life history and habits of Parasitellus fucorum, a mite associated with bumblebees (Bombus terrestris). The report indicates that even vital, primary information on many key co-habitants of bees’ nests has yet to be found. P. fucorum lives, reproduces and dies entirely in the nests of bumblebees, and requires freshly collected pollen to mature from a juvenile nymph into a sexually mature adult. Once mature, female mites feed on pollen grains, whereas male mites are predatory and even cannibalistic, feeding on mite larvae and nymphs.

Apart from scrounging pollen from the bees, these mites do no harm to the bees themselves. Varroa mites, in contrast, suck the juices from honeybees while they are still helpless in their cells, and continue to do so throughout their lives. Mite-ridden bees put on less weight than healthy ones, live shorter lives and become prone to other infections.

Two brands of pesticide are effective against varroa, but bee-keepers are reluctant to over-use them in case the mites become pesticide-resistant. The solution could be to find a biological alternative: if, as Koulianos and Schwarz show, P. fucorum males attack other mites, there could be natural residents of beehives that will attack varroa mites, too.

The varroa mite originated in southeast Asia where it is a parasite of the eastern honeybee (Apis cerana). It was first discovered in Apis mellifera in 1960, and was first found in the United States in 1987. By 1992, it had spread to most of the continental US and also to the UK, where it is currently devastating commercial hives across the country.