The last instar larva and the pupa ofPtilocolepus extensusMcLachlan, 1884, an endemic of the Iberian Peninsula, are described for the first time. The final instar larva ofPt. extensusbears close resemblance to those ofPtilocolepus granulatus(Pictet, 1834), but the abdomen has a well-developed dorsal sclerotized plate on segment VIII; this is a morphological feature which has not been observed in any other Ptilocolepinae. Final instar larvae make dorsoventrally flattened, elongate-oval cases of leaf pieces from several moss and liverwort species; such cases are characteristic of the Ptilocolepinae. Some additional data on biology and geographical distribution are given.