crithidia

1 capitalized :  a genus of flagellates of the family Trypanosomatidae that are exclusively parasites of invertebrates especially in the digestive tract of insects and that occur typically as elongated forms morphologically like trypanosomes but pass through developmental stages all in a single host in which they are indistinguishable from typical leptomonas and leishmanias

2a:  any flagellate of the genus Crithidiab:  any flagellate of the family Trypanosomatidae when exhibiting a typical form of a crithidia