Noah the Varroa

Here's something really gross: A live blood-sucking bee mite.

This little critter is magnified 80 times. It keeps moving it's front right leg upwards towards its mouth, which are the two smaller protuberances just above the moving leg. With each swing of its leg it's trying to hook onto a bee and stick its fangs into the bee's body. Yuck!
These little pests are called Varroa mites. I've called this one Noah the Varroa but it's not male, it's a female mite that is about 1.5 mm in diameter. She's just dropped off a bee and wants to climb back into the hive to continue feasting.
These little blood-suckers were originally pests of Asian honey bees but they hopped on to our honey bees a few decades ago and now they are endemic. Besides sucking the blood of adult bees they breed on the baby bees. Worse still they spread viruses that cause birth defects.
Left untreated Varroa mites kill bee colonies, so every few months I check my hives for mites. Over the last 10 days I've been collecting mites that drop off the bees on to a board under the hive. In winter a mite drop of more than 2 per day means treatment is necessary.
My two colonies dropped of 0.5 mites per day and zero mites per day respectively, so treatment is not indicated.
But that figure of zero has me worried. Either the bees have no mites, or I have no bees. I need to investigate further.