Insect sexing strains that produce only males under certain conditions are highly advantageous for genetic control programs. If larval diet is a major cost for a mass rearing factory it is desirable if female insects die at early stages of development. For building such strains it would be ideal if the gene promoter used to drive a conditional transcription factor (e.g. tTA) was only active at the embryo stage. However, identifying such promoters is not a trivial exercise. In our recent paper in Scientific Reports we show that promoters that are active throughout development can be used to build sexing strains with most of the females dying at early larval stages.