The Role of the Haemocytes in the Growth and Moulting of An Insect, Rhodnius Prolixus (Hemiptera)

Abstract

Moulting in Rhodnius is greatly delayed by the injection of trypan blue, indian ink or iron saccharate, which are taken up by the phagocytic blood cells (amoebocytes). This delay occurs only when the injections are made during the first 3 days after feeding, not on the fourth day or later. On the fourth day after feeding the amoebocytes become filled with secretory vacuoles which restrict the uptake of indian ink or iron saccharate. When the amoebocytes are blocked by such injections within a day after feeding, the secretory activity of the thoracic gland is greatly reduced. This is proved histologically and experimentally. On the other hand, moulting induced by implantation of a fully active thoracic gland is not delayed by blocking the haemocytes. It is therefore concluded that some substance secreted by the haemocytes is necessary for the full activity of the thoracic glands. The crystalline hormone isolated by Butenandt & Karlson from the silkworm will induce moulting in the decapitated Rhodnius larva and in the isolated abdomen. Its action is not inhibited or delayed by the injection of indian ink or iron saccharate. This supports the conclusion that it is the product of the thoracic gland. Sublethal high temperatures will inhibit moulting in Rhodnius even when it is provided with abundant hormone by injection of the crystalline material or by joining in parabiosis with a moulting larva.