Abstract Larvae of Catachlorops (C.) rufescens (Fabricius) were sampled in streams in the municipalities of Iranduba, Manacapuru, Manaus, Novo Airão, Presidente Figueiredo, and Rio Preto da Eva in the state of Amazonas, Brazil. Sampling was conducted in 2002 and between July 2007 and October 2008. Larvae were found entangled in sand on the underwater roots of riparian vegetation. A total of 169 larvae were collected, from which 93 were reared to obtain 64 imagoes (33 males and 31 females). The larval and pupal stages lasted an average of 88.2 days (±64.7) and 12.6 days (±2.9), respectively. A total of sixteen larval instars were estimated according to Dyar's Law. The larva, pupa and adult male were described, while bionomic data were provided for the larval stage under natural and controlled environmental conditions. [ABSTRACT FROM AUTHOR]