The beetle isn't slimy. The slime comes from the larvae who are eating and pooping through honey stores and brood.
They're speedy little critters that are easy to crush with your hive tool, but hard to sting, if you're a bee.
They fly into the hive and try to lay eggs in uncapped (I think) cells. The bees will try to chase them out. They'll scurry into crevices where the bees can't reach. The bees set up a guard, and try to keep them corralled in place.
Usually the beek inadvertently releases the beetles from their jail when she opens the hive for an inspection.
When eggs are laid, and larvae have eaten their fill, the larvae make their way out of the hive to pupate in the soil. They can apparently crawl a long way, so putting the hive on a concrete slab isn't enough to stop the cycle.
Once the mature she emerges from the soil, she flies back into the hive, and the cycle continues.