The grasshopper Euprepocnemis plorans plorans caused a considerable damage to crops of the Nile Delta, Egypt. The present study was conducted aiming to assess the insecticidal and anti hormonal effects of Precocene II on this grasshopper. The newly moulted 2nd or 4th penultimate instar nymphs were exposed to a series of doses 60, 40, 20 and 10 µg cm2. Exposure of 2nd instar nymphs to the higher two doses resulted in complete mortality of nymphs within 24 h. At the lower two doses, PII exhibited a considerably extended low toxicity on the subsequently moulted instars and emerged adults. LD50 was calculated as 0.388 µg cm2. After exposure of the 4th instar nymphs to PII, no complete mortality was observed, but various mortality percentages among the treated nymphs, 5th instar nymphs and adults. LD50 was calculated as 17.022 µg cm2. PII exerted a slight inhibitory action on the nymphal growth of both 4th and 5th instars, after treatment of 2nd instar nymphs, regardless the dose level, but the growth rate was remarkably regressed after treatment of 4th instar nymphs with 40 and 20 µg cm2. Exposure of 2nd instar nymphs to PII led to 3.33 precociously moulted nymphs into 4th instar, skipping off the 3rd instar only at the lowest dose . After exposure of 4th instar nymphs to PII, some treated nymphs precociously metamorphosed into adultoids, omitting the 5th instar, only at the higher tow doses. Another noticeable feature of the deranged development was permanent nymphs which induced in 2nd instar nymphs 3.85 after exposure only to 20 µg cm2. Also, similar permanent nymphs were induced during the 4th instar. No permanent nymphs had been induced after exposure of 4th instar nymphs to PII. K. Ghoneim | A. Basiouny "Insecticidal and Anti-juvenile Hormone Activities of Precocene II against the Grasshopper Euprepocnemis plorans plorans (Charp.) (Orthoptera: Acrididae)." Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-1 | Issue-6 , October 2017, URL: https://www.ijtsrd.com/papers/ijtsrd4603.pdf