Hydnophytum is a genus of epiphytic myrmecophytes (ant plants) native to Southeast Asia, the Pacific region and also extending into Queensland in northern Australia. 
 
Ant plants are so named for the fascinating symbiotic relationship they have developed with ants. Hollow, smooth-walled tunnels form within the caudex (trunks) of ant plants that provide a home for ant colonies. When dissected, you can see that ant plants naturally form a twisting labyrinth that mimics the inside of an underground ant colony. The ants that inhabit this bespoke home provide defense for the plant and prevent tissue damage, swarming to defend their home if disturbed. Ant colonies also provide nutrients to the plants by leaving wastes within the tunnels of the caudex. Special glands lining the tunnels then absorb nutriment for the plant. This symbiosis allows the plants to effectively gather nutrients (via the ants) from a much larger area than the roots ever could cover.
 
Despite the wonderful mutualism that occurs in nature, ant plants can be easily cultivated without ants in a home or greenhouse. In fact, their cultivation is quite similar to epiphytic orchids.
 
*A note about ant plants and false scale: many ant plants species may show signs of scale insect infestation on their leaves. However, there is no actual scale infestation. Rather, this is another aspect of their unique symbiotic relationship with ants. In the wild, ants eat--or sometimes farm--scale insects. By creating the appearance of scale insect damage, the ant plant is attempting to attract ants to move into its caudex.