Giant water bugs (aquatic Heteroptera), Belostoma dilatatum (Dufour, 1863), were collected in rice plantation water canals, in the Municipality of Eldorado do Sul, outskirts of Porto Alegre, State of Rio Grande do Sul, southern Brazil. Five specimens were dissected with the objective of finding metacercariae of digenetic trematodes. Four of them (80%) were positive for metacercarial cysts of Stomylotrema vicarium Braun, 1901. The intensities of infection varied from 1 to 16 metacercariae per host (average 7.6). The cysts were whitish, translucent, and found loose among the viscera, in the abdominal and thoracic cavities. Belostoma dilatatum is a new host record for metacercarial cysts of stomylotrematid digenetic trematodes and this is the first time that aquatic hemipterans are recorded as second intermediate hosts of digenetic trematodes in Brazil.
Heteroptera; trematode; Neotropical; Rio Grande do Sul; South America
