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The Mediterranean fruit fly Ceratitis capitata Wied. is one of the world’s most destructive fruit pests. Sustainable control is difficult due to its polyphagy, invasiveness, high eradication and containment costs, and the development of insecticide resistance (Giunti et al. 2023). Its presence in Bulgaria was first documented by Katinova et al. (2019). Understanding the species’ defence mechanisms is crucial for effective management. As haemocytes play a key role in insect immunity and development, this study examined their composition and dynamics during the larval development of C. capitata to support the future development of biological control strategies. A laboratory population of C. capitata from Thessaloniki (Greece) was maintained in a controlled-environment chamber. Synchronized prepupae reared on an artificial diet (Boller 1985) were used. Haemolymph was collected from 100 individuals per larval instar (first, second, third, and prepupal). Haemocyte types were identified morphologically, and their relative proportions were determined by differential counts. Four adjacent fields (0.02 mm² total) formed one sampling unit, and counts were taken at 10 randomly selected locations per slide. Significant differences between haemocyte type proportions among larval stages were assessed using the χ²-test and the z-test. Six distinct haemocyte types were identified in C. capitata hemolymph: prohaemocytes, plasmatocytes, granulocytes, oenocytoids, podocytes, and spherulocytes. Haemocyte composition varied significantly across the four larval stages (Chi-square = 2796.12, df = 15, p < 0.001). Pairwised z-test showed also significant difference between each haemocyte share during the four larval stages. Prohaemocytes increased steadily from 13% in L1 to 17% in the prepupal stage, indicating active haematopoiesis. Spherulocytes remained rare and relatively stable (1% in L1 to 0.05% in L4), suggesting a maintenance function. Podocytes rose sharply in L3 and L4, reaching 34% of all haemocytes, likely associated with morphogenetic processes. Oenocytoids were consistently low, highest in early stages - 5% in L1 and declining to 1% in L4, consistent with metabolic and detoxification roles. Plasmatocytes and granulocytes peaked in L3 (35% and 33% respectively), corresponding to maximum immune activity, followed by a slight decline in L4. Overall, the haemocyte profile shifted markedly with larval age, reflecting key physiological processes such as immune responses and preparation for metamorphosis.