Dugpas (Tib.). Lit., “Red Caps,” a sect in Tibet. Before the advent of Tsong-ka-pa in the fourteenth century, the Tibetans, whose Buddhism had deteriorated and been dreadfully adulterated with the tenets of the old Bhon religion,—were all Dugpas. From that century, however, and after the rigid laws imposed upon the Gelukpas (yellow caps) and the general reform and purification of Buddhism (or Lamaism), the Dugpas have given themselves over more than ever to sorcery, immorality, and drunkenness. Since then the word Dugpas has become a synonym of “sorcerer”, “adept of black magic” and everything vile. There are few, if any, Dugpas in Eastern Tibet, but they congregate in Bhutan, Sikkim, and the borderlands generally. Europeans not being permitted to penetrate further than those borders, the Orientalists never having studied Buddho-Lamaism in Tibet proper, but judging of it on hearsay and from what Cosmo di Köros, Schlagintweit, and a few others have learnt of it from Dugpas, confuse both religions and bring them under one head. They thus give out to the public pure Dugpaism instead of Buddho-Lamaism. In short Northern Buddhism in its purified, metaphysical form is almost entirely unknown.
Source: H.P.Blavatsky - The Theosophical Glossary