Most terrestrial isopods are ground-dwelling, scavenging detritivores, and rarely eat live vegetation. Here we report field and laboratory observations of the semi-terrestrial South African isopod, Tylos capensis Krauss, feeding above ground on live green leaves of the bietou bush, Chrysanthemoides monilifera (L.) Norlindh. The factors involved in the origin of this unusual arboreal feeding behavior are unknown, but we discuss three possible, not mutually exclusive, hypotheses that require testing: (1) Umhlanga beach, South Africa (our study site), provides insufficient detrital food to support the dense populations of T. capensis found in this area, thus causing these animals to seek out other food sources, (2) the relatively palatable and abundant C. monilifera leaves provide an easily accessible and digestible food source, and (3) few competing insect herbivores feed on C. monilifera leaves at Umhlanga beach, thus locally freeing up this resource for T. capensis.