Second instar larvae of Spodoptera littoralis were treated with LC1 0 level of delfin for 48 hours and with baythroid for 24 hours. The haemolymph of 5, 7, 9 and 11 days host larvae i.e. at 1, 3, 5 and 7 days after parasitism was then investigated. After 1 days of parasitism with Microplitis rufiventris Kok. where the egg stage was inside the host, no significant difference in the total haemocyte count (THC) was found between unparasitized and parasi‌tized larvae. After three days of parasitism, where the first larval instar of the parasite was inside the host larvae, the THCs of the parasitized larvae decreased insignificantly as compared to the healthy ones. While after five or seven days of parasitism where the second or third parasitic larval instars were inside the host, a highly significant decrease in THCs occurred as compared to those of unparasitized larvae. When healthy and paraSitized larvae were treated with LC10 level of delfin or bayth‌roid, THCs decreased significantly as compared to those of the control at different host larvae. Larvae of S.littoralis have eight types of haernocytes prohaemoc-ytes, phagocytic cells (palsmatocytes, spindle and granular cells), oenoc-ytoids, adipohaemocytes, spherulocytes and cystocytes. The phagocytic cells (palsmatocytes, spindle cells and granular cells) in parasitized larvae increased as compared to those of unparasi-tized ones of the same ages. While prohaemocytes of parasitized larvae became reduced in number as compared to those of unparasitized lar‌vae. The reduction in prohaemocytes may be due to prohaemocytes transformation into phagocytic cells. which are responsible for defense against invading organisms emphasizes their against the parasitoid. The spherulocytes and oenocytoids decreased in parasitized larvae than in the unparasitized ones. After treatment of parasitized larvae with delfin or baythroid, the phagoyctic cells increased more than those of unparasitized and parasi-tized larvae increased than those of control. During various developmental instars of S.littoralis larvae, the in-crease in haemocyte counts occurred in plasrnatocytes, granulocytes and oenocytoids While the prohaemocytes did not increase during de-velopment