ABSTRACT. — Bryocyclops maewaensis, new species, collected from a karstic cave in Lampang Province,
(northern Thailand), is described. The new species can be distinguished from its congeners by several
morphological characters, which include body ornamentation, the shape of anal operculum, three reducedsetae
on P4 endopod-2 of the female, and particularly the modifi ed spine on P3 endopod-2 of the male.
It is most similar to B. anninae (Menzel, 1926), originally described from moist moss in Java. This is the
fi rst record of the genus in Thailand and the second representative of cave-dwelling Copepoda there. This
species has so far been found only from pools fi lled with percolating water from the unsaturated zone of
a karstic aquifer.