cer·car·i·a 
(sər-kârē-ə)
(sər-kârē-ə)n. pl. cer·car·i·ae (-ē-ē′) or cer·car·i·as
A larva of a trematode, which develops from a sporocyst or a redia.
[New Latin cercāria : Greek kerkos, tail + -āria, feminine of Latin -ārius, -ary.]
cer·cari·al adj.