Published online by Cambridge University Press: 06 April 2009
1. The structure of the capitulum of I. ricinus L. is described briefly.
2. A stylet-like process is described in detail. Anteriorly it forms a distal attenuation, which widens out at its base near the point of attachment to the hypostome and is continued posteriorly as a distensible pouch overlying the pharynx. Anteriorly the stylet-like process is supported by a ventral sclerotized rod.
3. The stylet-like process effects closure of the pharyngeal orifice during contraction of the pharynx and so prevents the reflux of blood into the wound. In this it is assisted by the closure of the hypostomal gutter.
4. The stylet-like process appears to be a similar structure to that observed by Sen (1935) in three other species of Ixodid ticks and to be comparable in function to the tongue-like process described by Bertram (1939) in Ornithodorus spp.
The writer wishes to acknowledge his indebtedness to the Advisory Entomologist, Dr E. E. Edwards, in whose department the work was done; to Dr Alec Milne, Unit of Insect Physiology, Agricultural Research Council; Dr P. Tate, Molteno Institute of Parasitology, Cambridge, for reading the original script, for making many useful suggestions and modifications.