The trematode, Alloglossidium anomophagis sp. n. (Digenea: Plagiorchii
dae) exhibits progenesis in water fleas of the genus Daphnia (Anomopod
a: Daphniidae) occurring in temporary rainwater-filled ditches near Ho
uston, Texas, USA. We assume that A. anomophagis has achieved its trun
cated life cycle by eliminating the vertebrate which originally served
as the definitive host. The adults of A. anomophagis represent the sm
allest trematodes in the family Plagiorchiidae, measuring less than 0.
5 mm in length.