The present research quantified immune function (total and differential number of hemocytes, phagocytosis in vivo and activity of phenoloxidase) in the pupal stage of Carabus (Chaetocarabus) lefebvrei. Moreover, the cellular and humoral immune function was compared across the larval, pupal and adult stages to evaluate the changes in immunocompetence across the developmental stages. Four types of circulating hemocytes were characterized via transmission electron microscopy in the pupal stage: prohemocytes, plasmatocytes, granulocytes and oenocytoids. The artificial non-self-challenge treatments performed in vivo have shown that plasmatocytes and granulocytes are responsible for phagocytosis. The level of active phenoloxidase increases with the degree of pigmentation of the cuticle in each stage. In C. lefebvrei, there are different strategies in term of immune response to enhance the fitness of each life stage. The results have shown that the variation in speed and specificity of immune function across the developmental stages is correlated with differences in infection risk, life expectancy and biological function of the life cycle.