Colony collapse disorder has devastated bee colonies across the globe, but some bees will now have a built-in urge to fight back against varroa mites, a parasite that contributes to the mysterious phenomenon.

Researchers at Agricultural Research Service (ARS) have developed bees with a genetic trait that prompts them to aggressively seek out varroa mites and remove them from the brood nest. 

Varroa mites infest bee colonies, feeding on hemolymph, a combination of blood and fluid inside bees. Left untreated, the mites can kill entire colonies.

The genetic trait developed by ARS, called Varroa-sensitive hygiene (VSH), allows the bees to remove mite-infested pupae from developing bees that are sealed inside the honeycomb with a layer of wax.

VSH causes the bees to instigate a group battle against the mites, chewing through the wax cap and removing the infected brood and their mites.

The ARS team tested the effectiveness of this genetic trait by conducting field trials using 40 colonies with varying levels of VSH, finding that mite population was significantly lower in the bees with the gene.

A drastic rise in the number of honeybee colony disappearances was noticed in North America in late 2006, with the term ‘colony collapse disorder’ coined to describe the phenomenon.

Varroa mites – also known as ‘Vampire mites’ – are thought to be a major cause, though some researchers believe that environmental change-related stresses, malnutrition, pesticides and insect diseases are also to blame.