In a paper entitled ‘Crithidia sp., parasitic in the alimentary tract of Cenaeus carnifex’ (Gibbs, 1942), an attempt was made to describe a flagellate found in the mid-gut, hind-gut and rectum of a plant-feeding insect which is common in the Cape Peninsula, South Africa. It was shown that leishmanial forms and bodies described as mould-spores were carried around attached to the flagella of leptomonads. It was also observed that, in some form, the parasite was resistant to desiccation, as nymphs became infected when allowed to feed on the dried dejecta of infected insects. Large, fast-moving leptomonads were described as being the only forms found in the mid-gut, while smaller leptomonads with the attached bodies, as well as crithidial forms, were found in the hind-gut. The rectum was not studied on account of the difficulty then experienced in removing it unruptured.