Cotton (Gossypium sp.), belonging to the family Malvaceae, is one of the important commercial fibre crops of India as well as the world. Among the various limiting factors of cotton production, the insect pests are one of the major factors. In India, over 162 species of pests have been reported causing damage to cotton crop. Of the various pests recorded on cotton, the mealybug (Phenacoccus solenopsis), an invasive pest, has become a major threat in the cotton ecosystem. First time in India, Aenasius bambawalei Hayat - an endoparasitoid of cotton mealybugs reported to be a dominant parasitoid on Phenacoccus solenopsis in cotton but not much information is available on parasitic activity and its effectiveness against Phenacoccus solenopsis. Therefore, the present book highlights on Bionomics, Parasitic efficiency and Host stage preference by Aenasius bambawalei on cotton Mealybugs.