Licht-und elektronenmikroskopische Untersuchungen an Hodensekreten und Spermien der trombidiformen Milbe Abrolophus rubipes (Trouessart, 1888). - Anatomy of the testes, spermiocytogenesis and testicular secretory products of A brolophus rubipes (Erythraeidae) have been studied with the light and electron microscope. In the tubular testes a dorsal part producing germ cells, and a ventral portion constituting a reservoir for spermatozoa and secretory products can be distinguished. The wall of the latter is built up by large E. R. rich glandular cells. Three types of secretory products, all of which are of protein nature, are described, two of which take part in the construction of the spermatophore. The spindle-shaped spermatozoa possess a thread-like nucleus, which is surrounded by mitochondria (crista-type); in the periphery smooth-walled cisterns occur. The spermatozoa are covered by type I of the secretory products. Finally, the spermatocytogenesis of this species is described.