Photoperiod in Relation to Diapause in Hypera postica1 from California

Treatment of larvae of the alfalfa weevil, Hypera postica (Gyllenhal), from the Western United States with short (9 hours of light) photoperiod tended to result in fewer diapausing adults. Diapause was broken sooner when the adults were kept under a short photoperiod. Long (16 hours of light) photoperiod treatment of the parents resulted in fewer diapausing progeny.