Introduction

There are more than 800,000 species (kinds) of insects and still many more are discovered every year. The body of an adult insect has 3 main parts - the head, the thorax (or chest) and the abdomen. Almost all adult insects have a pair of feelers or antennae, at the front of the head. Every adult insect has six legs and most of them have one or two pairs of wings. The thorax is the locomotion center. It is packed with powerful muscles which operate the insect's 6 legs as well as its wings.

An adult insect wears its skeleton outside its body. This tough shell is light so the insect can still fly. The skeleton acts like a raincoat and keeps water from soaking into the body and from leaving the body! It protects the insect from heat and cold and from some of its enemies. Even though most butterflies and moths can glide for short periods of time most flying insects have thin wings and must beat their wings rapidly in order to get the lift they need. Bee's wings move forward, backward and up and down. Bees flap their wings over 100 times a second. The tiny "midge" beats its wings up to 1000 cycles per second! What is the purpose of flying? It is to carry pollen, flee from enemies, capture food, and mate.

How Insects Fly

Insects were the first creatures to develop wings. Since the wings are a part of the insect's back, or external skeleton, they do not develop until adulthood, just in time to mate. Originally, all winged insects had four separate wings as do all dragonflies today. But more recently, most insects, that have four wings, flap them together and have connected wing surfaces. For example, a Cicada Killer-Wasp rows through the air with a figure eight motion on wings coupled together by a "zipper". The wings are feathered like oars on the upbeat; on the downbeat, they spank the air-flat on; in-between they start to twist in anticipation of their next upward stroke. Other insects either have only two wings or only use two of their four wings to fly.

A dragonfly beats its pairs of long, slender wings independently, the front ones rising as the rear ones fall. In spite of this, the dragonfly is able to fly more than 35 mph, hover or even fly backward!

In the past, insects were observed by scientists after being put into glass jars. Recently, insect flight data has been collected by watching insects fly while tethered (tied). Scientists are able to watch the wing movements and calculate (figure out) how much oxygen and body fuel are used up. The wings actually rotate in a "figure 8" which then acts like a propeller. The stream of air goes downward and backward pushing the insect forward. You could describe the wing movements as vibrations rather than "flapping" as a bird would do. Scientists found that many insects can keep beating their wings for many hours!

Insects with high wing beats per second are able to keep this going because of kinetic energy (motion) passed on from one beat to the next between nerve impulses.

Even today, all insects are wingless when they hatch out of the egg. Since an insect's external skeleton has no stretch, the growing animal must molt (cast off) its old skeleton from time to time and grow a larger one. For winged insects there must be one final molt into winged form, since wings cannot be molted or replaced.

Butterflies and Moths

Upon touching a butterfly's wing, you will find a fine dust will come off on your fingertips. This dust comes from row upon row of tiny scales that cover the wings. It is these scales that make the lovely designs of color and light.

Most insects go through four distinct shapes or stages as they grow from egg to adult. A worm-like creature called "larva" develops from a tiny egg. When the larva has grown as big as it will grow, it attaches itself to a twig or any other suitable place fit for a long rest. We call the insect in this resting stage a "pupa". The pupa develops a covering called the pupal case. Inside this case, during the long pupal rest, the body of the adult takes shape. Many insects, however, skip some of these stages.

The butterfly and the moth take all four forms - egg, larva, pupa, and adult. The crawling caterpillars are the larvae of butterflies and moths. Caterpillars eat so much that their skins become too tight. All they have to do is split their skins and crawl out in new skins that fit better. They do this 4 or 5 times before becoming pupas.

Moth and butterfly larvae spin thin houses, or cocoons, around themselves for the pupal stage. Once the adult body is fully formed, the pupal case opens. Out comes the adult butterfly or moth. The wings quickly grow strong in the fresh air. In a few hours the adult insect can fly away. Insects have many enemies even among other insects. They protect themselves by hiding from sight or behind their own coloring. But sometimes the best defense is to just fly away!

Butterfly Migration

Butterflies as well as birds are fine fliers. But would you believe that these light and graceful creatures can cover long distances? Some species of butterflies migrate in search of warmth. The Monarch Butterfly can migrate more than 2000 miles (3200 km.) yearly.

The lovely orange and brown monarch butterfly leaves Canada every fall to fly thousands of miles southward. They often stop for a month in Natural Bridges state park in Santa Cruz (Northern California). Great swarms of them reach the Gulf of Mexico and even farther south. They spend the winter resting quietly in the sun.

In the spring they start the long journey back again. As they travel, the females lay their eggs on the milkweed plants. The eggs eventually develop into butterflies, who also fly north. Many of the older butterlies do not survive the long journey, but the young, strong butterflies carry on the pattern of migration. Many of these migrations are made over large bodies of water. Many species of butterflies migrate in large numbers, sometimes in the millions.

Ancient Insects

With one exception, all of the orders of insects represented in the Triassic age (225 million years ago) are alive today, an example of adaptibility (able to change) not seen among the higher animals.

There are six reasons insects have been able to survive and adapt (change) through the ages (millions of years):