Effect of ligation and ecdysone on total haemocyte count in the tobacco caterpillar, <i>Spodoptera litura</i> (Noctuidae: Lepidoptera)

Total haemocyte numbers in Spodoptera litura were studied under normal conditions and after ligation and subsequent injection of β-ecdysone. In late fifth stage larvae, ligation just behind the thorax resulted initially in a decrease of the total haemocyte count (THC) in both anterior and posterior halves, but 48 h postligation cell numbers increased in the anterior half, probably because of the presence of prothoracic glands in this region and also the elaboration of new cells from the anteriorly situated haemopoietic organs. The THC continued to remain low in the posterior half because of the deficiency of β-ecdysone and lack of haemopoietic organs. Injection of 50 μg of β-ecdysone into the "hormone-deficient" posterior half resulted in a significant increase in the haemocyte count, presumably because of direct or indirect hormonal stimulation of mitotis in circulating haemocytes.