A GENETIC STUDY OF THE COLOUR FORMS FOUND IN POPULATIONS OF THE GREENHOUSE RED SPIDER MITE, TETRANYCHUS URTICAE KOCH

There are two forms of greenhouse red spider mite in Great Britain, one with green summer females and the other with reddish brown females. The latter, usually associated with carnations, does not hibernate. Breeding experiments show that these forms are subgenerically distinct, but hybrids of low fertility can occur. The reddish colour of these female hybrids is incompletely dominant over the green and under some conditions they are indistinguishable from the reddish brown form. Biological information suggests that the British reddish brown form is distinct from Tetranychus cinnabarinus Bois.