gallfly

[gawl-flahy] /ˈgɔlˌflaɪ/
noun, plural gallflies.
1.
any of various insects that deposit their eggs in plants, causing the formation of galls.
Origin
1815-25; gall3 + fly2
British Dictionary definitions for gallfly

gallfly

/ˈɡɔːlˌflaɪ/
noun (pl) -flies
1.
any of several small insects that produce galls in plant tissues, such as the gall wasp and gall midge