gecko (gĕk´ō), small or medium-sized lizard of the family Gekkonidae. The more than 300 species are distributed throughout the warm regions of the world, mostly in the Old World. Despite folklore to the contrary, their bite is not poisonous. Many species are arboreal, while others inhabit human dwellings. Most lack movable eyelids and have characteristic pads on the undersides of their feet that enable them to cling to smooth surfaces and to run upside down on ceilings. The pads contain microscopic backward-projecting hairs covered by tiny pads that may generate an adhesive force through van der Waals attractions. Geckos are unique among lizards in that they possess voices, and different species make characteristic sounds. They feed on small animals, chiefly insects. Nearly all lay eggs. In Florida there are several introduced West Indian species as well as the widely distributed Turkish gecko, Hemidactylus turcicus, originally from Africa. Geckos are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Squamata, family Gekkonidae.