DEVELOPMENTAL BIOLOGY OF THE CARMINE AND GREEN FORMS OF TETRANYCHUS-URTICAE KOCH (ACARINA, TETRANYCHIDAE)

The reproductive biology of the carmine and green forms of Tetranychus urticae Koch from apple orchards in the western Cape, South Africa, was studied on apples and beans. The reproductive potential of the green form was lower on bean leaf discs than that of the carmine form, but was similar on apple leaf discs. The green form of T. urticae in South African apple orchards is thought to have developed through chemical selection, and that its poor adaptation to beans is coincidental. The minimum threshold temperature for development of the two forms was similar and was not influenced by host plant.