A study on sex-determination and karyotypic evolution inTetranychidae

The chromosome complements of 45 species of spider mites (Tetranychidae) were studied, making the total number of species now examined in this family 57, approximately 10% of all species known. The chromosome numbers range fromn=2 ton=7. The modal number of the family is 3 (found in 44% of the species). It is argued that the ancestral number isn=2 (21% of the species).In the more primitive subfamily of theBryobiinae both thelytokous and arrhenotokous species occur, whereas the subfamily of theTetranychinae exclusively exhibits arrhenotoky. The karyotype evolution is discussed in connection with arrhenotoky. It is stated that karyotype information is a useful tool for the spider mite taxonomist.This study was financially supported by the Netherlands Foundation for the Advancement of Tropical Research (W.O.T.R.O.) and the Uyttenboogaart-Eliasen Foundation.