Class Insecta: Characteristics & Orders

Class Insecta: Characteristics & Orders
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  • 0:04 An Overview of Class Insecta
  • 0:40 General Characteristics
  • 2:53 Five Common Insect Orders
  • 5:04 Lesson Summary
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Lesson Transcript
Instructor: Wendy McDougal

Wendy has taught high school Biology and has a master's degree in education.

Class Insecta contains all insects and belong to the phylum Arthropoda. It is the most diverse group of organisms on earth. Learn more about insects, both their similarities and their differences.

An Overview of Class Insecta

The earth is literally crawling and buzzing with insects, otherwise known as members of the class insecta. It would be hard to get through the day without a close encounter with a six-legged species. Insects are so prolific that added together they outnumber all other life forms combined. They are found on land, in the air, and in the sea. And the diversity is astounding. From the minuscule pesky flea to the majestic monarch butterfly, there are around a million different species. In spite of their vast differences, all insects have certain traits in common.

A variety of insects
Variety of Insects

General Characteristics

Insects belong to the phylum arthropoda, which means literally ''jointed legs''. As you may have guessed, this is one trait seen in all arthropods, including insects as well as animals like arachnids (spiders) and crustaceans (crabs).

Before delving into the characteristics of insects, it is important to clarify one point. People often refer to insects as bugs, but this is not always true. While it would be correct to say that all bugs are insects, we cannot say that all insects are bugs. True bugs belong to an order of their own, which we will discuss in a bit.

Now let's look at the structure of insects. An insect body is divided into three general regions: the head, thorax, and abdomen. On the head, we find a pair of antennae and eyes. These can be either simple or compound or even both, depending on the species. For instance, a dragonfly has two compound eyes, while houseflies have both simple and compound eyes.

Compound eyes on a dragonfly
Dragonfly with compound eyes

Also on the head we find specialized mouthparts that are used for chewing, sucking or even piercing, depending on the organism. These mouthparts are a major factor used in the classification of insects. For example, the grasshopper has a mandible that it uses for chewing grasses, while a flea has piercing and sucking mouthparts.

Chewing mouthparts of grasshopper under magnification
Grasshopper head magnified

The thorax, or midsection, contains those features that make it possible for the insect to get around. You probably already know that insects have six legs, setting them apart from eight-legged arachnids. These three pairs of legs are attached to the thorax, as are one or two pairs of wings. Unless, of course, the subject is of the non-flying variety, such as lice and fleas.

The abdomen is the final segment of the body, and is often large and bulbous. Within the abdomen are important internal structures such as the digestive system and reproductive organs, and this is also where stingers on stinging insects are found. Insects also have a skeleton, but it is on the exterior of their body and is therefore an exoskeleton. Made of a tough material called chitin, you may have attempted to step on a beetle only to find that it is essentially protected by a coat of armor.

Five Common Insect Orders

We have established that there are too many types of insects to cover in this lesson, nearly thirty orders in all. So, here we will take a look at five of the more common orders. First, the most prolific: order coleoptera. This is the massive group of beetles and also weevils, containing around 500,000 species. With hard exoskeletons, thick wings and chewing mouthparts, these insects are tough and versatile.

Ladybug, member of Coleoptera
Ladybug

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