Observations on the Life History of Triodontophorus tenuicollis, a Nematode Parasite of the Horse

Abstract

1. During the free-living development the larvæ of Triodontophorus tenuicollis undergo two moults separating three larval stages, the last stage remaining ensheathed in the cuticule of the previous stage.2. The development takes about four days when the eggs are cultured in horse fæces and charcoal at 26° C.3. The infective or third stage larvæ are climbers, and also show a marked resistance to desiccation ; they can also withstand variations in temperature from – 8° C. to 60° C.4. They do not penetrate skin.5. Infection of the host is probably via the mouth during grazing.6. The fourth-stage larva is described. It is free in the lumen of the colon, possesses a well-marked larval buccal capsule and three stout and pointed œsophageal teeth. Sex differences are now present.7. The adult buccal capsule develops in the form of a vesicle round the base of the larval buccal capsule.8. The probable mode of its parasitic development is given.9. A fourth-stage larva, probably that of either T. brevicauda or T. serratus, is described.