Abstract
In the report III (1954) of this series, I reported the experimental results of some investigations carried out during the summer season from July to August 1952-1953. Through these former investigations, I came to understand many points of the migration towards vegetables of the hookworm larvae. However it was unexpected that most of them were easily destroyed by the sun's rays after migration onto vegetables. Such frailness of the hookworm larvae, which climbed up the vegetables under the sunlight, may be a matter of course in their nature that the infective larvae of Ancylostoma duodenale perished at all within 24 hours at 40°C (Fujita and Mihara, 1951) .
During the summer season, therefore, the hookworm larvae should be destroyed by the sunlight that was more intense than in any other season and the effect of the ultraviolet rays may be harmful to them. Even Ascaris ova, which have a strong resisting potentiality against various influences in the natural world, are comparatively shortlived under the scorching sunbeams.
Now I have thought “what will happen to inf ective larvae after migration onto vegetables under a mild climate of a year” or “would nothing be killed during the spring season ?” and then I determined to pursue this question in spring from April to May 1955.
