The first detailed description of larvae of Ptecticus Loew is presented for P. brunettii and P. flavifemoratus from West Malaysia. There are pronounced morphological and behavioural differences between the last larval instar, inside whose cast cuticle the pupa remains, and earlier instars. The larval mouthparts are similar to those of other known Stratiomyidae larvae but may display a set of autapomorphic characters. The structure of the mandibular-maxillary complex suggests that larvae of Ptecticus are micropantophagous scavengers that feed chiefly upon microorganisms. The larvae of both species are associated with decaying bamboo shoots; P. brunettii inhabits the space between the culm sheaths and P. flavifemoratus lives in water-filled shoot stumps. This is the first record of aquatic Sarginae larvae and egg plastron in the Stratiomyidae. The life cycle and behaviour of P. brunettii and P. flavifemoratus is described and the resource partitioning of stratiomyids and xylomyids associated with bamboo is discussed.