They are very small and live where there are brains.
Some are pacifists, and they simply cause the brain to degenerate. Others are predatory; they eat the brain bit by bit, then join together to form one large insect and live inside.
We observed this phenomenon in Men in Black.
Added 1 minute ago
You can also try using a vacuum cleaner, again, in the ears.
Amko, why do you think that way? Do you have something against brains?