After many years of open discussion and development, the first genetically modified (GM) insect strains are entering field trials. A key engineered trait renders the insects “genetically sterile”, such that some or all of their offspring die; the insects additionally carry a fluorescent marker gene for easy identification. Such “genetic sterility” transgenes (in genetic terms, conditional dominant lethal genes) are not able to establish or spread in the wild due to their high fitness cost; such self-limiting strategies are widely viewed as the lowest risk category. Other genetic strategies are in development, including more invasive genetic systems. Some of these, such as those based on artificial infection with Wolbachia, may not be covered by regulations narrowly focused on the use of recombinant DNA technology despite having many similar properties.