Observations on a trypanosomatid flagellate in a flea, Peromyscopsylla silvatica spectabilis.

The method of attachment of a trypanosomatid parasite to the cuticular epithelium of the hindgut of a flea Peromyscopsylla silvatica spectabilis by a desmosome-like structure is described; the flagella are modified and have enlarged intraflagellar areas which occupy the whole surface area of the gut, including clefts and folds of the epithelium. Unusual features of the parasite itself include a very much reduced flagellar pocket and pellicular microtubules which are made up of doublets and triplets. The problems of differentiation and characterisation of monogenetic insect flagellates are discussed in the light of these findings.