Egg hatching at different temperatures and relative humidities in Idaea inquinata (Scopoli) (Lepidoptera Geometridae)

Idaea inquinata (Scopoli) mainly feeds on dried plants, nevertheless, it is also a potential pest of stored produce as it is able to develop on cereal products. The few references on the biology of this species do not deal with the influence of temperature and relative humidity on egg hatching. To fill this gap, groups of 100 eggs, 24-48 hours old, were exposed to five constant temperatures (17, 21, 26, 29, 34±1°C), two relative humidities (35, 70±5%) and a photoperiod of 0:24 (light:dark); ten tests were carried out. Each test was replicated four times and egg hatching was observed daily. The highest number of hatched eggs was observed at 26 and 29±1°C, 70±5% r.h. (91.5 and 91.0, respectively). The lowest number of hatched eggs was observed at 17°C and 70±5% r.h. (61.5). The mean number of hatched eggs (83.5, 77.5, 78.5, 79.8) is similar at 21, 26, 29 and 34±1°C, 35±5% r.h., respectively). The eggs hatched between the sixth and the eighth day at all the temperatures tested, except for 17±1°C and 35±5% r.h., where hatching started on the twelfth day. At this temperature the duration of the hatching period increases with increasing humidity: 11 days at 35% r.h. and 15 days at 70% r.h.