The false chinch bug, Nysius natalensis Evans (Hemiptera: Orsillidae), is a pest of sunflower, Helianthus annuus L. (Asteraceae), in South Africa. Pest outbreaks usually occur in localized areas towards the end of the summer. No information is currently available to predict these outbreaks. The effect of seven constant temperatures, namely 15, 19, 26, 28, 31, 36 and 38 °C on its reproduction, development and survival was determined. Longevity decreased as rearing temperatures increased. The optimum temperature for oviposition was between 26 and 28 °C with a mean of 246 and 276 eggs/female at 26 and 28 °C, respectively. There was also a significantly greater longevity compared to the other temperatures evaluated. No eggs were laid at or below 15 °C. Nysius natalensis could not complete its life cycle at 15 °C. The most favourable temperature range for development was between 26 and 36 °C. There was a strong positive linear relationship between temperature and the rate of development of the egg and nymphal stages as well as total development. Nysius natalensis required temperatures above a lower threshold of 14.0 °C, 13.97, and 15.2°C 14.8 °C for completion of the egg and nymphal stages, respectively, and from egg to adult stage. Degree-days required to complete the embryonic, larval and egg to adult stages were 74.6, 200.0 and 270.3 °D, respectively.