[Anomotaenia brevis (Clerc, 1902) Fuhrmann, 1908, Cestoda Cyclophyllidae, parasite of Leptothorax nylanderi (Forster), Hymenopterous, Formicidae (author's transl)].

Cysticercoids recovered from hemocoele of the ant Letothorax nylanderi are examinated by light and electron microscopy. This examination proves that the Cestode is a Dilepididae. The structure of the cysticercoids is the same that another Dilepididae, Anomotaenia constricta. The cysticercoids observed are those of A. brevis, parasite of three species of birds, Dendrocopos major, D. minor and Garrulus infaustus. The contamination of L. nylanderi by A. brevis occurs before metamorphosis of the Ant. The adults of L. nylanderi infested by A. brevis cysticercoids are morphologically different from the others; their physiology and behaviour are also different. The mechanisms of the parasitic action on the larval stages of L. nylanderi are discussed.