Callirhytis seminator, the wool sower, is a species of gall wasp in the family Cynipidae.

The wasps only lay eggs on white oak trees and only in the spring.

They lay the egg in a gall, a round, white structure resembling a cotton ball.

Scientists do not know what the alternate wool sower wasp gall looks like.

[2] The wasps neither sting humans nor occur in such numbers as to damage the white oak trees.