an adelgid of the genera Adelges or Pineus whose feeding frequently causes deformation of the host tissues, e.g., conelike swellings or galls on the twigs of spruces and true firs, and also twig dieback and defoliation —note examples of gall adelgids include the Cooley spruce gall adelgid (Adelges cooleyi), the eastern spruce gall adelgid (A. abietis), and the balsam woolly adelgid (A. piceae) —see aphid This definition last updated 10/24/2008