The previously unknown larva of Elpiscladius capicola Harrison & Cranston (Diptera: Chironomidae: Orthocladiinae), predicted by postulated phylogeny to be associated with aquatic immersed leaves or wood, has been found. The larva is xylophagous, and occurs in a limited area of the Western Cape, in the Eerste River and Leopard's Kloof stream in the Hottentots Holland mountains. Association with E. capicola is assured by a distinctive (pharate) pupa visible within one mature larva, and the co-occurrence of larvae and diagnostic pupal exuviae in soft immersed wood. The characteristic mentum of Elpiscladius resembles that of Xylotopus Oliver, a Nearctic wood-mining genus, but other features including the dorsal head sclerites and the simple SI seta differ. Although phylogeny predicted the larval biology, addition of 17 larval features for Elpiscladius to that data matrix destroyed the relationship with Austrobrillia Freeman, reducing the Brillia group essentially to a polytomy. Larvae of Elpiscladius co-occur with the immature stages of an undescribed species of Stenochironomus (s.s.) Kieffer. Both these rare xylophagous taxa indicate clean flowing waters with intact native riparian vegetation, and thus can be regarded as biodiversity and environmental conservation indicators.