noun
dobsonfly; Protohermes grandis
Refers to a large aquatic insect of the Corydalidae family, especially the species Protohermes grandis found in Japan. The name literally means 'snake dragonfly' but it is not a dragonfly.
川の近くでヘビトンボを見つけた。
I found a dobsonfly near the river.
ヘビトンボの幼虫は水生昆虫を食べる。
Dobsonfly larvae eat aquatic insects.
トンボ means 'dragonfly', while ヘビトンボ is a different insect (dobsonfly) despite the similar name.
The name ヘビトンボ (蛇蜻蛉) literally combines 蛇 (へび, 'snake') and 蜻蛉 (とんぼ, 'dragonfly'), likely referring to the insect's long, snake-like appearance or its large mandibles. The exact origin is uncertain.