What is an invertebrate?

An invertebrate is an animal without a backbone.

We have many invertebrates living on the campus of The Elisabeth Morrow School. Click on the invertebrate to learn more about it.

• arachnids
• centipedes
• crustaceans
• insects
• millipedes
• mollusks
• worms

Each type of invertebrate has a very special body adapted for life in a certain habitat. Its body is also adapted for the niche it serves which helps it do its own very special job for the ecosystem it lives in. Each type of invertebrate also has its own special life cycle. Let's look at what this means.

Habitat is where the animal lives within its ecosystem. Habitat involves the space, water, food, air, including oxygen and carbon dioxide, minerals such as iron and calcium, and weather, including temperature and all that the seasons bring to the ecosystem.

Invertebrate habitats

• gardens
• soil
• leaf litter
• herbaceous (green) plants, shrubs and trees

Niches are the jobs animals perform for their environment. Many of these jobs are so important, that if the animal who performs it becomes extinct, all of us within the ecosystem will suffer.

Invertebrate Niches

• Decomposers: Earthworms, millipedes, carrion beetles, flies and their babies, maggots, are all decomposers. They feed on dead plant and animal matter. If there were no decomposers, all the plants and animals who have died would still be laying around on the ground and at the bottom of the rivers and seas. Life itself would stop. Within the decomposers live bacteria and other single celled organisms called protists, which help digest the dead matter. The nutrients locked in dead leaves and animals are then returned to the earth to be used by living organisms.
• Carnivores: Spiders, centipedes, crustaceans and many kinds of insects such as dragonflies and lady bugs are carnivores. They are meat eaters, feeding on living animals. Without carnivores to keep the animal populations down we would be overrun with pests. That little spider that lives in the corner of your garden catches many harmful invertebrates such as mosquitoes for its dinner. We need carnivores to keep the animal population in balance.
• Herbivores: Mollusks such as snails and slugs, insects such as grasshoppers and caterpillars help keep the plant population in balance. Without herbivores munching on leaves we would have no caterpillars. Without caterpillars we would have no new butterflies and without butterflies we would have few pollinators.
• Pollinators: Without this special job done by bees, butterflies, and many other kinds of insects, flowering plants would not be able to reproduce! Pollinators carry pollen from flower to flower of the same plant species. It is the pollen which fertilizes the plant, allowing it to create new seeds. Without pollinating animals, we would have no new flowering plants and without flowering plants we would not have enough producers making food for themselves and for the entire animal kingdom! We really need pollinators.

Invertebrates go through amazing life cycles from egg to adult. One of the most interesting is the life cycle of a butterfly. At The Elisabeth Morrow School we have planted a butterfly garden, with the host plants of lots of different caterpillars.

Our School Garden

The Monarch butterfly chooses a milkweed plant on which to lay her egg because her caterpillar will only eat milkweed leaves. We have several different kinds of milkweed plants in our school garden and have attracted Monarchs to our garden. The welcome mat is out all summer long.

• Metamorphosis: Butterflies go through complete metamorphosis, which means change of body, in four stages. Let's look at the metamorphosis of the Monarch butterfly.

1. Egg Stage: The adult butterfly lays her egg on the host plant, or the plant the caterpillar will eat once it hatches from the egg. The host plant for the Monarch caterpillar is the milkweed plant.

Monarch Butterfly Egg

 

2. Caterpillar Stage: The caterpillar hatches from the egg. It eats and eats and eats.

Monarch Caterpillar

It only stops eating the leaves of the host plant when it needs to shed its outer layer of skin which is called molting. It molts because its body has gotten too big for its skin. The monarch caterpillar is a beautiful yellow, white and black caterpillar. After it sheds it keeps eating until finally, after about 2 weeks, it goes into the next stage or pupal stage where it forms its chrysalis by shedding its final outer skin to reveal a beautiful jade green chrysalis patterned with golden points.

Monarch caterpillar shedding its final skin to expose the chrysalis.

3. Chrysalis Stage: Inside this lovely green box considered to be one of the most beautiful objects in the natural world, the caterpillar is changing into a butterfly. This process, which takes about a week to ten days, has been described as a time when the cells of the caterpillar's body is similar to that of tomato soup! The cells of the body are being rearranged to form the cells of the butterfly's body.

Monarch Chrysalis

4. Adult Stage: The day that the butterfly will emerge from its chrysalis, the chrysalis turns from green to clear so that you can see the orange and black patterns of the Monarch butterfly.

Chrysalis right before butterfly emerges.

It takes about 20 minutes for the butterfly to emerge from the chrysalis. It hangs from the now empty chrysalis and flaps its wings so that the blood is pumped throughout the wings to give them strength. The Monarch butterfly then flies off to a flower to feed on nectar. It will go right to the milkweed flowers if they are nearby. It also loves butterfly bush, goldenrod, and butterfly weed.

Newly emerged butterfly feeding on the nectar of goldenrod.

The life cycle is now complete. The butterfly will mate and then lay her egg on a milkweed plant and the cycle starts all over again.

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