Involvement of vitamin A in the photoperiodic induction of diapause in the spider mite Tetranychus urticae is demonstrated by rearing an albino mutant on a semi‐synthetic diet with and without p‐carotene or vitamin A

Data are presented on the development from egg to adult of a wild‐type and an albino strain of the spider mite Tetranychus urticae on a semi‐synthetic liquid diet.The diet is a modification of the diet developed by Van der Geest et al. (1983).Apart from the standard diet without added carotenoids, diets supplemented with either β‐carotene or vitamin A were tested.A high incidence of diapause was found in the wild‐type strain under short‐day conditions on all three diets.No diapause was found in the albino mutant under short days on the standard diet.Partial restoration of the photoperiodic response was obtained after addition of β‐carotene to the diet, and full restoration was found after the addition of vitamin A.Diapause could be terminated in diet‐reared diapausing females of both strains after a cold rest of 3 weeks at 4°C.The results lead to the conclusion that vitamin A or a derivative of vitamin A probably functions as the photoreceptor pigment for the photoperiodic induction of diapause in the spider mite.