Although the driving force is not exactly clear, several species of Australian origin insects have become invasive within the last decade (Quadrastichodella nova Girault, Epichrysocharis burwelli Schauff, Ophelimus eucalypti (Gahan), O. maskelli (Ashmead), Aprostocetus sp., Nambouria xanthops Berry & Withers, Leptocybe invasa Fisher & La Salle, Moona spermophaga Kim & La Salle, Leprosa milga Kim & La Salle). Recently, a new gall wasp, Selitrichodes globulus La Salle & Gates has joined a growing list of invasive species. Since 2000, L. invasa is wreaking havoc on eucalyptus plantations throughout the world. First reported from northern and eastern Africa, the Middle East and Mediterranean countries, the pest has expanded its range in every continent. First reported in 2001 from Mandya district in Karnataka, the pest has now spread to neighboring states of Kerala, Tamil Nadu and Andhra Pradesh and recently it has also been reported from North India. Another invasive gall wasp, O. maskelli is ravaging eucalyptus in several Mediterranean and southern European countries. Apart from gall wasps many insects of Australian origin have become a major constraint in eucalyptus production throughout the world. Increasing trend towards travel and import of plant products suggest that exotic species will continue to invade India in future with unprecedented consequences. Growers, conservationists, researchers, and regulatory authorities share identical commitment to mitigate and prevent unwanted invasions. With potentially hundreds of species of insects recorded on eucalypts, one could expect more of these species to become invasive in future. With second highest area under eucalyptus in the world, India is a potential destination for range expansion for some of these invaders. Annually, alien species cost millions of rupees in control measures and crop damage. Neither the resources nor the management structures are adequate to solve the problem. While time and money are limited and the number of introduced species continue to increase the study and control of invaders cannot be sustained on a case-by-case basis. These questions need to be attended by taking a fresh look at the invasive pest species and the science of 'Invasion Biology'.