The embryology of Lytta viridana Le Conte (Coleoptera: Meloidae). III. The structure of the chorion and micropyles

This paper deals with the morphology of the chorion and associated structures in the egg of Lytta viridana as observed through the light microscope and the electron microscope. The chorion proper is a thin, single layer exhibiting a delicate banded pattern at high magnification. The micropyles are extremely complex protrusions of the chorion, having central cavities from which flap-like arms extend at various angles. These flaps exhibit the same banding pattern as the chorion, although the periodicity is more variable. Exterior to the chorion is found a frothy mucilaginous material which holds the eggs together in a clump after they are laid. Between the chorion and the vitelline membrane a thin layer of homogeneous material is found in laid eggs. The peculiar characteristics of these structures are compared with those of other insect eggs, and their significance in connection with water conservation, respiration, and sperm entry is discussed.