One of the important characteristics elevating Heliothis spp. to major pest status is the ability to enter facultative diapause. Diapause maintains populations during periods when hosts are unavailable or conditions are not conducive to reproduction and population survival. Development resumes in spring with the onset of warmer temperatures and moth emergence becomes concentrated. Survival of overwintering populations and the contribution of this carry over of moths to the development of populations the following season are not well established in Australia. Overwinter survival studies for H. punctigera and H. armigera were conducted in south-east Queensland to investigate differences between the two species.