Abstract
Northern populations of Aedes sierrensis (Ludlow) (Diptera: Culicidae) undergo long-day induced embryonic diapause in the summer as well as short-day induced 4th instar diapause in winter. Photoperiod experienced by the parental generation has no effect on embryonic diapause. The duality of the photoperiodic response confers univoltinism on populations exhibiting both embryonic and larval diapause.