The Biology and Morphology of Crithidia acanthocephali n. sp., Leptomonas leptoglossi n. sp., and Blastocrithidia euschisti n. sp.*

Three new species of Trypanosomatidae were isolated from three species of bugs: Leptomonas leptoglossi from Leptoglossus phyllopus, Crithidia acanthocephali from Acanthocephala femorata, and Blastocrithidia euschisti from Euschistus servus. All were cultured axenically and on avian embryo membranes. In addition to differences in morphology the three organisms displayed different growth rates in the chorio‐allantoic fluids of duck and chick embryos incubated at 30°C. L. leptoglossi grew most abundantly. B. euschisti barely maintained itself while C. acanthocephali occupied an intermediate position. When the temperature of incubation was raised to 37°C, there was continued multiplication of L. leptoglossi and C. acanthocephali, but there was no growth of B. euschisti in either duck or chick embryos. It is suggested that the criteria of morphology, cultural characteristics in vitro and in vivo, plus physiological characters be used as future aids in classification of the Trypanosomatidae.