noun
leaf beetle (subfamily Donaciinae)
Refers specifically to beetles of the subfamily Donaciinae, often found near water.
ネクイハムシは水辺の植物の根を食べる。
The leaf beetle (Donaciinae) eats the roots of waterside plants.
The name is composed of 根 (root), 喰い (eating), and 葉虫 (leaf beetle), literally 'root-eating leaf beetle'. The exact derivation is uncertain, but it likely describes the larval feeding habit.