What are the four types of insect hemocytes?

• A. Prohemocytes, plasmatocytes, granular hemocytes, and cystocytes
• B. Prohemocytes, plasmatocytes, granular hemocytes, and oenocytoids
• C. Prohemocytes, plasmatocytes, lamellocytes, and granulocytes
• D. Prohemocytes, plasmatocytes, granular hemocytes, and cystocytes

Answer: (A)

Insect blood cells come in several specialized forms that carry out different immune tasks, starting from undifferentiated prohemocytes that serve as precursors. As these cells differentiate, they produce plasmatocytes, which are the main phagocytic cells that ingest pathogens and help coordinate immune responses. Granular hemocytes, with their internal granules, contribute to encapsulation, coagulation, and defense reactions by releasing enzymes and other factors. The fourth type in this classification, cystocytes, completes the commonly taught quartet of hemocyte types in many insect texts. Together, these four cover the primary functional roles—precursor supply, phagocytosis, granule-based defense, and encapsulation/related responses—that circulate in insect hemolymph. It’s worth noting that some texts use different names (for example, oenocytoids or lamellocytes) in related classifications, but in this item the set includes cystocytes as the fourth type.