Descriptions are given of all developmental stages of Dyscinetonyssus hystricosus n. g. n. sp., an associate of the dynastine scarabaeid Dyscinetus trachypygus Burmeister. The developmental chaetotaxy of the legs, venter and dorsum of the mite is described and, in the case of the leg and dorsal chaetotaxy, utilized to demonstrate the existence of sexual dimorphism in all stages except the larva. The taxonomie placement of Dyscinetonyssus within the Laelaptoidea is discussed.