Animals have two ways to make sure that they leave offspring in the world, so that their genes survive. One is to have few children and care for each one intensely. The other is to have huge numbers of offspring, so that even though many die enough survives. That is what insects do. Most of those eggs, or the larvae they give birth to, will die in one way or another, so there have to be many of them.
In most insects, life begins as an independent egg. This type is reproduction is known as ovipary. Each egg is manufactured within the female's genital system and is eventually released from her body through an ovipositor, a tube-like, saw-like, or blade-like component of her external genitalia. The egg-laying process is known as oviposition. Each insect species produces eggs that are genetically unique and often physically distinctive as well - spherical, oval, conical, sausage-shaped, barrel-shaped, or torpedo-shaped. Yet regardless of size or shape, each egg is composed of only a single living cell.
In most insects the egg is covered by a protective "shell" of protein secreted before oviposition by accessory glands in the female's reproductive system. This eggshell, called the chorion, is often sculptured with microscopic grooves or ridges that may be visible only under the high magnification of an electron microscope. The chorion is perforated by microscopic pores that allow respiratory exchange of oxygen and carbon dioxide with relatively little loss of water. The micropyle, a special opening near the anterior end of the chorion, serves as a gateway for entry of sperm during fertilization.
A female receives sperm from her male partner during the act of mating. She can store that sperm for long periods of time in a special part of her reproductive system, the spermatheca. As a developing egg moves past the opening to the spermatheca, a few sperm are released onto its surface. The sperm swim toward the micropyle - the first one to reach its destination enters and injects its nucleus into the egg. The sperm nucleus quickly fuses with the egg nucleus to form a one-celled embryo. This event is known as fertilization. After the egg is fertilized, it undergoes a period of rapid growth and development known as embryogenesis, literally the "embryo's beginning".
Many insects pass the winter in the egg stage. Insect eggs are ideally suited for withstanding the hardships of winter. The eggs have shells that are thick and watertight. In many cases the eggs are covered with hairs, silk, or frothy materials produced by the female before she died. These provide an extra degree of protection by insulating the eggs. Most butterfly or moth caterpillars eat their eggshell just after the hatching as they get maximum proteins out of eggshell. But these “Baby Bugs” just crawling here without eating the eggshell.