All species of sundew are able to move their tentacles in response to contact with edible prey. The tentacles are extremely sensitive and will bend toward the center of the leaf to bring the insect into contact with as many stalked glands as possible. According to Charles Darwin, the contact of the legs of a small gnat with a single tentacle is enough to induce this response. This response to touch is known as thigmonasty, and is quite rapid in some species. The outer tentacles (recently coined as "snap-tentacles") of "D. burmannii" and "D. sessilifolia" can bend inwards toward prey in a matter of seconds after contact, while "D. glanduligera" is known to bend these tentacles in toward prey in tenths of a second. In addition to tentacle movement, some species are able to bend their laminae to various degrees to maximize contact with the prey. Of these, "D. capensis" exhibits what is probably the most dramatic movement, curling its leaf completely around prey in 30 minutes. Some species, such as "D. filiformis", are unable to bend their leaves in response to prey.