Egg Stage

Fertilization take place right before the egg is laid.

If you had a powerful microscope, you could see small holes in the chorion (shell) that allow sperm to enter. These holes are called the micropyle. The micropyle is the only entrance for sperm. There are eight holes centered around a central opening.

Can you see the rosette markings around the micropyle?

These are sperm guides that direct the sperm towards the entrances.

19 hours after fertilization

The Manduca embryo grows around the yolk mass. The chorion and yolk have been removed and the developing head can be see in the micrograph to the left.

When viewing the egg with a hand lens, you can see variation in color. Newly laid eggs are blue-green. As the embryo develops it becomes pale in color and near the end of embryonic development, a black stripe can be seen through the chorion; this is the horn.

If you had a powerful microscope you could observe the body wall begin to broaden and segment. The mouthparts begin to form and you can start to see the new spiracles (entrance to the breathing tubes). After the first 37 hours the embryo begins to develop quickly.

The embryo starts to look more familiar. The body wall has grown up and around the yolk mass. You can see the well-developed legs and the beginning of the head.

During that time, the insect will undergo a shedding of the cuticle while it is still enclosed within the chorion.

The insect will emerge by using its mandibles to chew a hole in the chorion and crawl out. It will devour the entire chorion before moving to the plant. Here is a newly emerged larva showing the head and you can also see the eyes and antennae.