Entomology is a branch of zoology that focuses on the study of insects. It is a taxon based category and covers all the scientific studies which are related to insects. Some of the common insect categories which are dealt with in this field are Coleoptera, Lepidoptera, Hymenoptera and Diptera. One of its major sub-disciplines is economic entomology, which studies the harmful and beneficial effects of insects on humans and their activities. Entomology plays a vital role in the study of biodiversity and in analyzing the environmental quality. This textbook attempts to understand the multiple branches that fall under the discipline of entomology and how such concepts have practical applications. Some of the diverse topics covered herein address the varied branches that fall under this category. In this book, constant effort has been made to make the understanding of the difficult concepts of entomology as easy and informative as possible, for the readers.