The Penetration of the host tissue by the harvest mite, Trombicula Autumnalis shaw

Abstract

1. The introduction refers to the fragmentary state of our knowledge on Trombiculid mites and indicates that most attention has been devoted to the taxonomy and bionomics of the group. The life cycle and general method of feeding are briefly outlined and reference is made to previous work directly concerned with the present treatise.2. The morphology of the organs related to the phenomenon of piercing and sucking in the larva of Trombicula autumnalis is described.3. The physical factors of the skin influence the choice of habitat upon the host.4. The food consists of tissue fluid and disintegrated cells of the malpighian layer partially liquefied by the action of injected saliva, a condition typical of extra-intestinal digestion.5. The mechanism of the initial piercing of the skin, which is done by the cheliceral claws, is described.6. A tubular tissue canal is gradually formed in the skin of the host and around its insoluble wall are deposited superimposed layers of keratinized protective tissue.7. The mechanism of suction is described and the factors which play a part are considered. The problem of the tissue canal serving as a duct for both the ejection of saliva and the suction of food is explained by the alternation of the two processes. The inter-relationship, between the intermittent injections of saliva, the formation of the tissue canal and the deposition of protective tissue, is elucidated.