Fig. 4

Mean of minimum temperature from October to March in France between 1969 and 2011 (indicator of the larval feeding activity; Robinet et al. 2007). This temperature is based on the mean temperature in 2000 calculated over the grid covering France and the mean annual deviation recorded over ten weather stations. The grey line gives the yearly temperature and the black line gives the moving average over 10 years. Despite large fluctuations of the yearly temperature, the 10-year average temperature increased noticeably in the early 1990s and remained relatively stable since the early 2000s