The role of the haemocytes in the growth and moulting of an insect, Rhodmus prolixus (Hemiptera

Growth and moulting in insects is initiated by a hormone produced in the neuro-secretory cells of the brain. This brain factor activates the thoracic (or ' prothoracic') glands, which are then believed to secrete the definitive 'growth and moulting hormone'. These conclusions are based chiefly on experiments with Rhodnius (Wigglesworth, 1940,1952a), Lepidoptera (Fukuda, 1944; Williams, 1947), Diptera (Possompes, 1953) and Megaloptera (Rahm, 1952), and there is abundant histo-logical and experimental evidence from other groups which points in the same direction (see Wigglesworth, 1954). The possibility remains, however, that there may be yet further links in the chain of endocrine organs, located, for example, in the abdomen. The object of the present work was to investigate this possibility in Rhodnius. The chief organs in the abdomen in Rhodnius are the gut and Malpighian tubes, the heart and pericardial cells, the gonads, muscles, nerves and sense organs, the fat body, dermal glands, oenocytes and the haemocytes of various kinds. The gonads are not necessary for growth; the oenocytes and the dermal glands reac