The white lady spiders of the Namib: pale, long-legged dune huntsman spiders that drum the sand to communicate across distances, navigate hundreds of meters of featureless desert at night, and return to burrows by dead reckoning that researchers study as a model of animal navigation.
Honesty governs the keeping note: dune specialists translate poorly to containers. They need deep fine sand, arid heat, night activity, and space the drumming assumes, and the captive record is thin and humbling. Not medically serious; genuinely difficult.
Namibian supply is nearly nonexistent, listings are rare singles, and prices form on pure scarcity. The genus trades on its biology to keepers who accept that they are attempting a desert in a box, and the drumming, if it comes, is the reward.