Genus Vol. 11 (4): 527-539 Wroc³aw, 26 XII 2000 A description of the late-instar larva of Nossidium pilosellum (MARSHAM, 1802) (Coleoptera: Ptiliidae) ALEKSANDRA KILIAN 1 and BOLES£AW BURAKOWSKI 2 1 Zoological Institute, University of Wroclaw, Sienkiewicza 21, 50-335, Poland, e-mail: alkagath@biol.uni.wroc.pl 2 Zoological Institute and Museum, Polish Academy of Sciences, Wilcza 64, 00-679, Warszawa ABSTRACT. A detailed description of the late-instar larva of Nossidium pilosellum (MARSHAM) is given, the illustrations of structural features provided. The differences in morphological structures between the larvae of N. pilosellum and N. americanum MOTSCHULSKY are mentioned. Key words: Entomology, morphology, larva, Coleoptera, Ptiliidae, Nossidium pilosellum. INTRODUCTION Featherwing beetles are the smallest known beetles including over 400 known species with estimates of the probable total greatly exceeding this number (DYBAS 1976). Family Ptiliidae HEER belongs to the leptinid association distin- guished by BÖVING and CRAIGHEAD (1931) on the basis of larval characters. The Leptinid association includes larvae bearing primitive characters such as: mandible with asperate or tuberculate molar part, maxilla with fringed galea, urogomphi present two- or one- jointed and anal membrane furnished with anal hooks. Larvae of Ptiliidae have been previously described or mentioned by PERRIS (1853, 1862 - Ptinella aptera GUÈRIN, Acrotrichis intermedia (GILLMEISTER)), MATTHEWS (1872 - Actinopteryx MATTHEWS), BÖVING and CRAIGHEAD (1931- Nossidium ERICHSON) and HINTON (1941 - Acrotrichis fascicularis HERBST) who mentioned also larvae of Ptinella limbata (HEER) as previously described, but did