Egg hatching at different temperatures and relative humidities in <i>Idaea inquinata</i> (Scopoli) (Lepidoptera: Geometridae)

Abstract

Idaea inquinata (Scopoli) feeds mainly on dried plants, nevertheless, it is also a potential pest of stored products 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 and 34±1°C), two relative humidities (35 and 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 mean number of hatched eggs was observed at 26 and 29±1°C, 70±5% r.h. with 91.5 and 91.0 eggs, respectively. The lowest mean number of hatched eggs was 61.5 observed at 17°C and 70±5% r.h. The mean numbers of hatched eggs, 83.5, 77.5, 78.5 and 79.8 were similar at 21, 26, 29 and 34±1°C, 35±5% r.h., respectively. 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 increased with increasing humidity: 11 d at 35% r.h. and 15 d at 70% r.h. Keywords: Egg, Hatching, Temperature, Relative humidity, Rusty wave moth