The South American tomato pinworm,Tuta absoluta, (SATP) is now a devastating pest worldwide of crops in the family Solanaceae. Most prior studies of SATP's thermal biology were based on populations from tropical regions, and proved unsuitable for explaining its invasion of large areas of the Palearctic. A more holistic approach to the analysis of its thermal biology is essential background for developing models to assess its invasive potential. Our studies found that SATP has lower and upper thermal thresholds(theta(L) = 5.37 degrees C and theta(U)= 35.69 degrees C, respectively) than South American populations used in prior studies (theta(L)= 7.38 degrees C and theta(U)= 33.82 degrees C). Age-specific life tables were used to estimate the effects of temperature on its demographic parameters. Diapause in SATP had not been characterized prior to our study. We found facultative diapause in pupae developing from larvae exposed to relatively low temperatures (i.e., 2 and 5 degrees C) and short-day length for different exposure periods. The strength of diapause was measured as an increase in post-treatment developmental times of pupae (i.e., degree days) that on average were 2.45-3-fold greater than of pupae reared at favorable temperatures. A lower developmental threshold and a facultative diapause increase the invasive potential of SATP in temperate areas. Knowledge of this thermal biology is essential for predicting the potential geographic spread of this pest and to develop management and control strategies.