Abstract
Seven trematode metacercariae are reported as natural infections in aquatic arthropods. One, which develops precociously to maturity free in the body cavity of Hetaerina americana (Odonata), is described as a new genus and species, NEOPROSTHODENDRIUM progeneticum. Another, which occurs encysted or free in the hemocoel of gomphid naiads (Odonata), belongs to the genus Eumegacetes. Other metacercariae were not identified beyond the family level, but are described and/or figured as an aid to further life history studies.
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