Moulting and morphogenesis of sensilla in a prostigmate mite (acari, actinotrichida, actinedida: caeculidae) I. Mechanoreceptive bristles.

In the prostigmate mite Microcaeculus steineri delamarei moulting and morphogenesis of mechanoreceptive sensilla were studied by electron microscopy and compared to corresponding sensilla of other arthropods. Dendritic contact with the cuticular parts of old sensilla breaks down during apolysis. Two groups of cells are engaged in the formation of new sensilla: 1) several trichogen and two tormogen cells in a semicircular arrangement, and 2) two sheath cells surrounding the mechanoreceptive dendrites. Cells ensheathing the dendrites do not play any part in the formation of bristles. These observations differ from those on insect sensilla during moulting.