Papilio demoleus is a common and wide spread swallow tail butterfly which is also known as lime butterfly. The butterfly is a pest and invasive species found from Asia to Australia. The caterpillars can completely defoliate young Citrus trees and also delicate citrus nurseries. Azadirachtin, the active ingredient of neem has been demonstrated to have an antecedent and insect growth regulatory effects, negative influence on the reproduction of female as well as reduction in oviposition and infertility of eggs. Neem excel 0.15% EC was tested on citrus leaves and treated on 4th and 5th instars of caterpillar of P.demoleus. Mortality was found highly significant at 0.1% level of significance. However other concentrations also revealed significant mortality percentage at 5% level of significance. Adult emergence was considerably affected by 0.04% concentration, which caused 64.44% emergence in comparison to 95.00% in control. Pre ovipostion and oviposion periods were significantly delayed while post oviposition period was shortened to 93.33 hrs at 0.04% concentrations. Fertility was found reduced and after hatching percentage of malformed individuals were increased.