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Spruce budworm is a major defoliator of forests in North America and its periodic outbreak can cause severe economic growth loss. In 2008, Vaidya and Wu proposed a delayed spruce budworm population model and studied the impact of physiological structure on outbreak control (Vaidya and Wu, 2008 [27]). In this paper, we revisit this model and study its global dynamics that has not been analyzed previously. By carefully dealing with the major difficulty caused jointly by the time delay and the nonlinearity, we give a rather complete stability analysis for the model, including global asymptotic stability, bistability, semi-stability and Hopf bifurcation. Moreover, we show that the time delay can induce interesting dynamics including multitype bistability and long transients. [ABSTRACT FROM AUTHOR]