THE EGGS OF FORFICULA-AURICULARIA L (DERMAPTERA, FORFICULIDAE) - ULTRASTRUCTURE AND RESISTANCE TO LOW AND HIGH-TEMPERATURES

The morphology, ultrastructure, and resistance to low and high temperatures of the fertilized egg of Forficula auricularia were studied both before and after water absorption. The increase in volume resulting from water absorption did not modify the ultrastructure of the envelopes. The chorion was found to be made of five distinct layers and of a vitelline envelope under which a serosal cuticle was secreted by the embryo. Before hydration, the supercooling point of the egg was -27-degrees-C; after hydration, it was -22-degrees-C. Hydration did not alter the resistance of the egg to heat. It withstood a thermal rise to 36-degrees-C without apparent damage. Morphological and physiological changes due to water absorption did not result in a modification of the viability of the eggs when they were exposed to temperature differences.