Spatial distribution and hatch times of egg masses of gypsy moth (Lepidoptera: Lymantriidae)

The influence of the position of egg masses of the gypsy moth, Lymantria dispar (L.), on a tree bole on hatching time was investigated at field sites in Ontario and Pennsylvania. Although eggs were deposited predominantly on the eastern sides of tree boles, egg hatch was most advanced in masses located on southern sides. There was no strong relationship between height on the tree bole and rate of egg hatch, especially for the lower portion ( 2 m) of the bole. Eggs deposited under bark flaps experienced a significant delay in hatching compared with eggs deposited on the bark surface. Within egg masses, eggs from the bottom third of the mass hatched slightly later than those from the middle or top thirds of the mass. Understanding the microclimatic variables that influence hatch times will improve the accuracy of prediction of the phenology of this forest pest