Participate in the firefly event between 0-6 and 18-24 o'clock, go to the forest island, and wave your handheld insect trap at the flying saw-horned snow fireflies to generate bubbles.
When bubbles are wrapped around it, you can catch the Saw-Horned Snow Firefly.
It can be seen from the illustration: Sawhorn Snow Firefly needs to participate in the firefly event between 0-6 and 18-24 o'clock, and can be caught on Forest Island.