To provide a thermal volatilizing system applicable to a conventional electric mosquito-repellent tool equipped with a heat radiating plate having the nearly same area as that of a mat, usable together with a conventional mat for one day and capable of sustaining stable insecticidal efficacies over a long time of ≥5 days.

This insecticidal mat for a long time is obtained by laminating a pulp plate or a plastic plate having 1.5-3.0 mm thickness, a length in the longitudinal direction nearly equal to that of the mat, the length in the transverse direction of 0.3-0.6 the overall length of the mat and ≤0.30 Wm-1K-1 thermal conductivity at 300 K from one lateral end in the transverse direction to the inside onto the base of the mat made of a pulp and having 20-24 mm length, 32-38 mm breadth and 2.0-3.0 mm thickness. The resultant laminate having a clip for fixing the mat in one lateral end in the transverse direction comprises ≥50 mg of a pyrethroid insecticidal ingredient and a volatilization regulator in a weight ratio of ≥0.3 based on the pyrethroid insecticidal ingredient. The thermal volatilizing insecticidal method comprises using the insecticidal mat.