Hemocytes of Insects: Their Morphology and Function

Hemocytes are blood cells that circulate in a clear fluid, the plasma, within the hemocele (body cavity) of insects. The hemocytes, plasma, and dissolved inorganic and organic molecules constitute the hemolymph. Nutrients, nitrogenous waste products, hormones, and a variety of other substances also are transported in the hemolymph for distribution to various tissues. In most insect larvae, the hemocytes are produced within hematopoietic (hemopoietic) organs (blood cell producing factories) where they replicate and differentiate. The number and types of hemocytes vary with insect species, developmental stage, and physiological state. In general, total hemocyte count (the number of hemocytes per unit volume) increases throughout larval development, reaching a maximum at each larval ecydsis but probably not during pupal/adult ecdysis. Qualitative and quantitative fluctuations in hemocyte populations also may be influenced by endocrine events as well as by wounding and microbial and...