A new species of Temnocephala Blanchard, 1849 is described from southern Brazil, ectosymbiont on giant water bugs (aquatic hemipterans), Belostoma spp. from the greater Porto Alegre, State of Rio Grande do Sul. Some hemipterans examined were positive for this species of Temnocephala and carried bunches of eggs between the first two pairs of legs and between the first pair of legs and the rostrum, as well as adult and young specimens. The adults were darkly pigmented (greenish-brown), mimetizing the color of the hemipteran hosts. The new species is similar to Temnocephala decarloi Moretto, 1978, from Argentina, the only other species of Temnocephala from belostomatid hemipterans known to date, by having an extra long and curved cirrus, but differs by having the distal portion of the introvert not bent as a 'full-bent' smoking pipe-like, as the author depicted originally for T. decarloi.
Ectocommensals; Neotropical; Rio Grande do Sul; South America; taxonomy
