In this study, an Adelina sp. (Coccidia) infection was determined for the first time from Anisoplia segetum (Coleoptera: Scarabaeidae). The infection was observed in the gut and fat body of the host. The determined oocysts were ellipsoidal and measured 36.3 (34-38) x 30.2 (27-32) mu m. The number of sporocysts per oocyst varied from 7 to 15. The dizoic sporocysts were usually subspherical, 10.2 (9-12) x 8.9 (8-10) mu m. Also, some developmental stages and unsporulated oocysts were determined with electron microscopical observations. The immature microgamonts were observed in different shapes, from ovoid to spherical. And the detected oval unsporulated oocyst was measured 4.9 mu m in length and 3.6 mu m in width. The formation and distribution of these pathogens were also presented in A. segetum populations.