Initiation and development of the stem gall induced by Hemadas nubilipennis (Hymenoptera: Pteromalidae) on lowbush blueberry, Vaccinium angustifolium (Ericaceae)

Abstract

Hemadas nubilipennis Ashmead, a tiny chalcid wasp, induces a multichambered, reniform gall at the tips of vegetative shoots of Vaccinium angustifolium Aiton (lowbush blueberry). The life cycle of H. nubilipennis and the anatomical changes occurring within the shoots during gall development are described. Growth of attacked shoots is terminated by growth of the gall. Some aspects of gall growth and development are similar to those of galls induced by cynipid wasps, even though chalcids and cynipids are distantly related. Proliferation of insect-induced gall cells begins before the eggs of H. nubilipennis hatch, and by the time the larvae begin to feed, they are surrounded by thick layers of parenchymatous cells. Nutritive cells are differentiated from gall parenchyma, and as the gall matures, a layer of sclerenchymatous cells is differentiated and circumscribes each larval chamber.