Tuesday, June 06, 2006

Butterfly Egg

Butterfly eggs consist of a hard-ridged outer layer of shell, called the chorion. This is lined with a thin coating of wax which prevents the egg from drying out before the larva has had time to fully develop. Each egg contains a number of tiny funnel-shaped openings at one end, called micropyles; the purpose of these holes is to allow sperm to enter and fertilize the egg. Butterfly and moth eggs vary greatly in size between species, but they are all either spherical or ovate.

Butterfly Eggs
Butterfly Eggs
The egg is the fertilized ovum of the female. Butterfly eggs are commonly yellow or green in color and may darken just before hatching. The shape of the egg may be spherical or oval and flattened. The chorion ( egg – shell ) is often beautifully reticulated / sculptured with ribs or pits. The egg is slightly depressed at the top and a small opening or micro Pyle is situated in it. Through the micro Pyle, the sperm enters the egg for fertilization and after the eggs are laid, air and moisture for the developing embryo pass through the micro Pyle only . egg yolk provides the food for the developing embryo.

Butterfly Eggs are always laid on or in the immediate vicinity of plants or any other food resource suitable for larval feeding. They are laid singly or in clusters, mostly on the upper surface of leaves or any part of the plant and a few species of butterflies scatter their eggs at random as they fly over vegetation. Frequently, eggs are laid on the undersurface of the leaf to protect them from rain, direct sunlight and to some extend predators. The female usually glues the eggs to the surface of the leaf or any substrate with a viscous secretion from her body. Female butterflies select the food plants for egg laying both by chemical and visual cues. Species of danaidae scratch the leaf to confirm the identity before laying eggs. Females avoid plants that already have eggs laid on them. Thus ensures that food is there for her eggs only.

The fully formed embryo of the developing larva can be seen through the transparent chorion, just before hatching. The young larva gnaws its way through the shell and after hatching, it eats the shell as it contains nutrients essential for the larva. After eating the shell, the larvae will start devouring the food plant. Generally the egg period lasts for 3 – 4 days.

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