In the present study, the toxic effect of three different natural essential oils of medicinal plants, namely Garlic (Allium sativum), Mint (Mintha pipereta) and Eucalyptus (Eucalyptus globulus) were tested on 1st nymphal instar of the grasshopper (Heteracris littoralis). The LC50 values of the tested oils were estimated after 14 days from feeding on treated diet mixed with different concentrations of the oil. The LC50 of the tested oils were arranged as follows: 0.067, 0.075 and 0.084ml. /100ml. diet for Garlic, Eucalyptus and Mint respectively. The effect of LC50 concentration of the oils on the biological aspects and histological changes that observed on the alimentary canal and fat bodies were recorded. The normal development of the grasshopper was exhibited. Results cleared that there was statistical variable numbers of increased the nymphal periods, life cycle, adults longevity and life span comparing with the control test. Garlic oil inhibited egg lying by the resulting females offspring of the treated1st instar nymphs. High reduction in the deposited eggs and egg fertility caused by Eucalyptus or Mint oil and marked malformation were observed. Histological changes on the alimentary canal and fat bodies of the remaining nymphs after treatment with Garlic oil (the most effective oil) were detected by the light microscope have been recorded. The results suggest that the natural plant essential oils of Garlic, Eucalyptus and Mint may be used in IPM control program against H. littoralis grasshopper.