Cuticular lobes in the Tetranychus urticae complex (Acari : Tetranychidae): a reliable taxonomic character?

Taxonomic work on spider mites has mostly been based on morphological characters. The shape of lobes on dorsal integumentary ridges of summer females was used in the past as an additional morphological character to discriminate between the green and the red forms of the two-spotted spider mite Tetranychus urticae. However, we showed that lobes were not always present or were not completely formed in some females, presumably because of micro-environmental conditions. No clear-cut differences were put forward between green and red forms concerning that ridge structure. This underlines the care needed when this criterion is used. The possible role of lobes in adaptation to water balance is discussed.