Monarch butterfly eggs

This model demonstrates the structure of eggs of a monarch butterfly. Monarch butterflies lay their eggs in spring or summer, on the underside of the Euphorbia leaf, closer to its top. Each egg forms inside the female before fertilization, including a hard outer shell called the chorion that protects the developing larva inside. The shell is covered with a layer of wax that prevents the eggs from drying out. The eggs have tiny funnel-shaped holes at one end called a micropile. These holes penetrate through the shell, allowing sperm to enter as the eggs form a hard shell prior to fertilization. The ridges on the eggshell are called ridges and are also formed before the eggs are laid. The dark head of a developing caterpillar can be seen at the top of the eggs before hatching. In the egg stage, the monarch butterfly lives from 3 to 5 days.