Cerebral larvae in the second intermediate host of Dicrocoelium dendriticum (Rudolphi, 1819) and Dicrocoelium hospes Looss, 1907 (Trematodes, Dicrocoeliidae).

Cerebral larvae of Dicorcoelium dendriticum and D. hospes and the brains of infected ants were studied. Morphologic differences of the freed larvae could not be found, but there were evident differences in number and localization of the cerebral stages. Ants infected with D. dendriticum usually showed one "Hirnwurm" while in the majority of the ants infected with D. hospes two larvae were found. The typical localization of the "Hirnwurm" of D. dendriticum was in the ventral part of the subesophageal ganglion; almost every larva of D. hospes was found in the dorsal part of an antennal lobe. The cyst walls of the larvae were visible only in some specimens. Their thickness seemed to depend on the localization of the larva. Differences in number and localization of the larvae, and hypotheticalmechanisms how they could influence the behavior of their hosts are discussed.