Present day has witnessed to the development of a new interdisciplinary subject. Chemical Ecology or Phytochemical Ecology, which is concerned with the biochemistry of plant & animal interactions. The development of' the plant-insect interaction increasingly successful due to identifications of organic molecules, particularly secondary biochemicals such as alkaloids, steroids, phenols & terpenoids, etc. A further stimulation has been the possible applications of such new information in the control of insect pest. Phenomenon of host plant specialization requires that an insect must be able to...