Abstarct: Blood cells are an important indicator of insect immunity against pathogens, parasitoid, starvation stresses, nutritional diets, sex, diapause and environmental factors such as temperature. Insects use of reactions of cellular and humeral defense in contrast to any stress or attacking of external agent. Hemocytes play an important role in cellular immune system of insects and have many forms and activities. Also, antimicrobial peptides, such as the phenol oxidase enzyme, are one main components of insects humeral defense. By accurate recognition of hemocytes condition and evaluating the activity of the phenoloxidase enzyme can be better understood the insect physiological defense aspects and these will help to adopt their physiological control strategies. In this study, firstly hemocytes of Indian meal moth, Plodia interpunctella (Hȕbner) were identified by staining with Giemsa and by light microscopy. The amount of enzyme activity of phenoloxidase was measured by method of hemocyte lysite in the presence of L-DOPA substrate and 1 molar phosphate buffer. Five types of hemocytes including prohemocytes (PRs), plasmatocytes (PLs), granulocytes (GRs), oenocytoids (OEs) and spherulocytes (SPs) were identified in larvae hemolymph of Indian meal moth. The frequency of hemocytes in 3td, 4th and 5th instar larvae showed that the number of PLs and GRs in the higher age of larvae were the most abundant. In addition, the total hemocyte count (THC) increased significantly in the higher age of larvae. The effect of starvation periods on THC was significant, and decreased significantly with the increase in the length period of starvation. The number of PLs and GRs decreased significantly after 72 hours of starvation. Increasing in the duration of starvation caused a significant decrease in the activity of the enzyme phenoloxidase. The results of the experiment on the effect of nutritional diets including pea and raisin, walnut, pistachios and artificial diet showed that the maximum THC, PLs and OEs were attributed to the larvae fed with pea and raisin. The amount of phenoloxidase activity in larvae fed on artificial diet was significantly higher than the other diets. THC in females was significantly higher than males and the frequency of each hemocyte except PRs in females was significantly higher than males. The activity of Phenol oxidase enzyme in males was more than females, but did not show any significant difference. The results of this study showed that the THC, differential hemocyte count (DHC) and amount of phenol oxidase activity in 5th instar larvae of Indian meal moth were largely influenced by starvation periods, nutritional diets and sex.