What is the preferred stage of bee Varroa mites target for their phoretic stage?

Varroa mites specifically target older nurse bees during their phoretic stage because these bees are more likely to have open brood where the mites can reproduce and thrive. Older nurse bees, typically aged around 5 to 12 days, are involved in caring for the developing brood, making them ideal hosts for the mites. The presence of brood provides an essential environment for the mites to feed and reproduce, as they can attach to these bees and then subsequently move to the brood cells to lay their eggs.

Newly emerged bees, while they do not present the same opportunity for the mites to reproduce, are still not the preferred stage for attachment since they are transitioning into their roles and are less involved with brood care. Foraging worker bees are generally too busy collecting nectar and pollen to be at the brood site necessary for the mites’ reproductive cycle. Drone bees, while they do provide a source for mite attachment, are not the primary target because they are less frequent in the hive compared to worker bees and serve a different role in the hive's lifecycle.

Therefore, the targeting of older nurse bees reflects a strategic advantage for the Varroa mite in maximizing their potential to reproduce and infest the hive effectively.