The mycetomal microorganisms of Sitophilus granarius (L.) (Coleoptera) are flexible, non acid-fast, non-flagellated rods, often surrounded by mucoid material. Pleomorphic and involution forms are present. Life cycle stages have been observed. The literature on these organisms is briefly reviewed. As they have never been cultured in vitro and the literature indicates this may be very difficult or even impossible, a postulate of Murray's regarding identification of symbiotes by morphology is invoked and the mycetomal microorganisms (plasmids, Blochmann bodies) in this insect are tentatively referred to the Myxobacterales (sens. lat.).