The pupa of Culex (Culex) bidens Dyar is described based on specimens from Mexico. The pupa is compared with the pupae of Culex (Culex) declarator Dyar Knab and Culex (Culex) interfor Dyar, similar species which are easily confused with Culex bidens.
Keywords: Diptera, Mexico, Culex bidens, Culex declarator, Culex interfor, pupa.