The Butterfly Egg Stage

The first of four stages - The Butterfly Egg Stage

The imago (i-ma-go) butterfly is able to reproduce immediately after the last ecdysis stage.

Ecdysis (ek'de-ses) is the last moulting for the chrysalis upon which emerges an adult butterfly.

Now being sexually mature, the female butterfly is ready to mate. By the 2nd or 3rd day most female butterflies have mated.

Life is short for many butterfly species therefore mating quickly is necessary. So quickly that males patrol for mates constantly. For example..

Photo: Eleaner

.. the Zebra Longwing male, are at the chrysalis of the female assisting removing her. Once the female is removed the male will mate with her then fly off.

It's similar with the Small and Clouded Apollo male butterflies. The female is not able to fly yet and the male mates with her once she emerges from her chrysalis.

After butterfly mating occurs the male flies off.

Butterflies are oviparous which is any animal, reptile or insect species that hatch from an egg outside of the mother's body. There is hardly any embryonic development, if any, that takes place inside the mother.

Larval development takes place inside the egg where embryonic cells produce tissue for organs that will be required during the second stage of metamorphosis. Inside the butterfly egg is the vitelline membrane which is the sac that shelters the developing larva, or caterpillar.

The first three stages of development - the butterfly egg, larva and chrysalis stages are referred to as the immature stage. Although each stage has different sets of genes, the genetic make-up remains the same throughout.

The egg is first produced in the female's ovary. The chorion is a hard protective shell which surrounds the egg. It is made of several thin layers producing one thick shell making it resistant to puncture and helping it retain moisture to protect the embryo. At one end there are small holes allowing the male sperm to enter. These holes also allow oxygen and carbon dioxide to pass through. These small openings in the chorion are called micropyles.

The female produces eggs within several tubular ovaries. These ovaries then lead through many lateral oviducts that meet and fuse to a single duct in her abdomen, the corpus bursa.

After mating, but before fertilization, the female stores the male's sperm in her corpus bursa. When the female passes the butterfly egg through her corpus bursa the egg then becomes fertilized.

Fertilization does not occur until the female finds the host plant
where she will deposit her butterfly egg or eggs.

After mating the female flies around finding shelter in a butterfly host plant where she can lay her egg or eggs.

She is able to locate the preferred host plant by tactile, olfactory and visual sensory cells found on prolegs and antennae. Host plants can be a tree, shrub or plant - including weeds.

Many plants serve as a hosts to most types of butterflies. There are a few butterfly species, however, where only one or two host plants will sustain them. With these exceptional species, if the butterfly egg is placed on the wrong host plant the larva will die because that host plant is not suited to them.

Photo: Suenorth

Once the female butterfly finds her chosen host site oviposition occurs. Oviposition is the process of the female laying one egg or several. In her lifetime, the female will lay 100 to 1000 eggs, depending on the butterfly species.

First the egg will pass through the sperm sac in the corpus bursa. After doing so the egg then becomes fertilized with both male and female gametes, or reproductive cells. Each egg then passes through her ovipositor, also known as the oviduct. This is the organ through which a female will deposit her eggs.

The number of broods a female butterfly will have also depends on the species. A brood refers to the number of eggs deposited at one time. It is noted that butterflies in warmer climates will have more broods than those from a colder climate where migration is necessary. Many butterflies in colder climates average two broods per season.

If many eggs are placed on a host plant it is called an egg cluster. Butterfly eggs may not necessarily be placed directly on the host plant, nor is it always an egg cluster.

For example, Fritillaries are known to drop their eggs on the ground close to dried violets. Fritillaries will also place eggs on plants next to their preferred host plant. Azure butterflies lay one egg at the flower buds of different host plants.

Interestingly with butterfly egg clusters,
once the caterpillars emerge cannibalism may occur.

Laying eggs one at a time in different locations will reduce the likelihood of cannibalism, helping to keep their population numbers strong for the next generation.

Colors and shapes of the butterfly egg vary depending on the species by the colleterial glands. The colleterial gland also produces a sticky, cement like adhesive that adheres the egg firmly to leaves. This substance is similar to wax offering protection to the egg so it won't dry out.