It was reported by SCHÄFFER (1889), OSHIMA (1935) and ARVY (1952, 1953) that hemocytes might arise from hemocytopoietic organs which were located near or attached to imaginal wing discs in some of the Lepidoptera. But, as JONES (1962) described in his recent review, the evidence for hemocytopoietic organs in insects was based entirely on histological evidence and experimental physiological proof was lacking.
In order to prove that the aggregations of cells attached to the imaginal wing discs in the silkworm are really hemocytopoietic organs, the present authors burnt every imaginal wing discs and the neighboring parts of larvae with a red-hot needle and observed the effects of such treatment on the counts of different kinds of hemocytes.
The death rate of the larvae, which had got burnt on their imaginal wing discs and the neighboring parts, was very high. And, it took two more days for the larvae got burnt than for the control larvae to grow into mature larvae.
As shown in the table, relative proportions of proleucocytes and plasmatocytes to total hemocytes disdrawn from the larvae, which had been burnt on their imaginal wing discs and the neighboring parts in the 2nd day of 5th instar, were far less than the ones from the control larvae. As the total number of hemocytes in a constant volume of hemolymph was not increased by the treatment, it was considered that the real numbers of proleucocytes and plasmatocytes were decreased as well as the relative proportions of them.
On the other hand, relative proportions of proleucocytes and plasmatocytes were not decreased by the treatment to burn larvae on their 1st and 2nd spiracles.
Total hemocyte counts from the wingless moths, which had been burnt on their imaginal wing discs and the neighboring parts in their larval stage, were less than the ones from the controlmoths. Relative proportion of plasmatocytes to total hemocytes were decreased by the treatment.
In addition, the present authors made sure of the fac that most of the cells in question did not ingest the particles of Indian ink which had been injected into larval body cavities.
As a result of the present experiments, it is suggested that the hemocytopoietic organs described by SCHÄFFER, OSHIMA and ARVY were proved experimentally to be real hemocytopoietic organs which form proleucocytes and plasmatocytes.