Effects of temperature on larval survival rate and duration of development in Lymantria monacha [L.] on needles of Pinus sylvestris [L.] and in L.Dispar [L.] on leaves of Quercus robur [L.]

This study assessed the effects of temperature on survival rate and duration of development (DD), i.e., time needed by larvae to reach the pupal stage, in nun moth (Lymantria monacha L.) and gypsy moth (L. dispar L.). The larvae were raised at 15, 20 or 25°C, and fed with current-year-needles of Scots pine (Pinus sylvestris L.) and leaves of English oak (Quercus robur L.), respectively. With increasing temperature 15, 20 and 25°C, larval survival rate (LSR) declined in L. monacha (for 35th day LSR was 0.44, 0.31 and 0.21, respectively), but increased in L. dispar (0.50, 1.00 and 0.94). In contrast, the duration of development decreased with increasing temperature in larvae of both moth species (67, 52 and 39 days for L. monacha, and 66, 43 and 33 days for L. dispar, respectively). The differences in larval survival rate between those species at higher temperatures can affect significantly their growth and development in warmer years. Therefore, it is possible that under global climate change these differences may lead to changes in distribution of both insect species.