Restricted distribution of Japanese land leeches (Haemadipsa japonica) on the Shikoku Island

Abstract

We conducted questionnaire and field surveys for the land leech (Haemadipsa japonica) on Shikoku Island, where the leech has been reported from a small area. A questionnaire survey was distributed to the staff of the Forestry Agency in Shikoku in October 2024. Further, a field survey was conducted at 24 sites in Naka town, Tokushima Prefecture, and the surrounding areas at the beginning of the month. Blood-sucking injuries surely by the leech in Naka and Kaiyo towns were reported in the questionnaire survey. The land leeches were found at 10 sites stretching in an area 19 km by 14 km during the field survey, which covered the western part of Naka town and the northern tip of Kaiyo town. The land leech expansion accompanied by over-abundant sika deer was expected, however, land leech distribution in Shikoku remained restricted in the area centering on the western part of Naka town.