1. A small insect, especially a wasp or midge, that lays eggs in plants and causes the formation of galls.
Usage: Also called gall wasp or gall midge depending on the species.

Examples

• The gallfly laid its eggs inside the oak leaf, triggering the plant to form a protective gall.
• Biologists study gallflies to understand how insects manipulate plant growth.
• A single gallfly can cause hundreds of galls to develop on a single tree.
• The gall produced by the gallfly provides shelter and food for the developing larva.