The haemolymph of Tettigonia cantans (Fuess) has been studied at the preimago and imago stages with both electron and light microscopic methods. PAS-negative granules were detected in histochemical reactions. On electronograms, one type of haemocytes was referred to as granulocytes recognized in haemolymph. In the cytoplasm of granulocytes, two types of granules were found: those of mitochondrial origin, and those being derivatives of the Golgi apparatus. Secret discharge is realized by the merocrine way. Four stages of granulocyte development are distinguished: the formation of granules and organelle development; the formation and accumulation of granules, active secretion, and cell destruction.