Animals > Arthropods > Insects
Insects: class Insecta
The rest of this chapter is devoted to a closer look at insects. The most important goal of this part of the lab is for you to look closely at some insects and understand their features. We’ll approach this goal by studying the features that differentiate the various insect orders from one another.
- Life history: Almost all insects molt, or shed their cuticle, periodically as they grow. At each molt, an insect’s body may go through a morphological change, until it finally reaches its adult form, in which it is sexually mature. After this, molting generally stops. There are two styles of insect development: hemimetabolous and holometabolous. Hemimetabolous insects go through a series of nymph stages, each stage looking a little more like the adult than the previous stage. Holometabolous insect go through a dramatic metamorphosis, passing though a pupal stage during which they break down almost all the structures in the larval body and use the materials to construct a new adult body.
- Mouth parts: Insects have complicated mouths. The mouth of an insect is formed from multiple parts See the Wikipedia article on insect mouthparts for more information and diagrams.
- Wings: Most kinds of insects have two pairs of wings. The wings normally appear only when an insect reaches the adult (reproductive) stage; larval or nymph stages don’t have wings. The form and function of the wings varies from one insect order to another. Many have membranous wings, which are thin and usually more or less transparent, and are functional for flying. In some insect orders, the wings may be thick and opaque (not membranous), or greatly reduced in size so that they don’t function for flying, or one or both pairs of wings may be missing entirely. See the insect order descriptions below for more specific descriptions.
- Antennae. Each insect has a pair of chemosensory antennae on its head, used for sensing chemicals in the air, water, or on solid surfaces. The antennae vary widely, from tiny (e.g., dragonflies) to huge and elaborate (as found in some beetles).
- Eyes: Insects normally have a pair of compound eyes, which are large and obvious. Many insects also have two or three ocelli, which are smaller, non-compound eyes. Antennae. Adult insects normally have one pair of antennae, which function as chemoreceptor and mechanoreceptor organs. The shape of the antennae varies greatly among the insect orders; for descriptions and pictures or the different styles, see http://en.wikipedia.org/wiki/Insect_morphology#Antennae.
- Appendages on the abdomen: Many insects have some sort of appendages on the posterior end of the abdomen.
Identifying insect orders:
There is a lot of diversity in the class Insecta. In this lab, you'll get an overview of some of that diversity by learning to identify a few orders of insects. To do that, you'll need to learn to recognize some of the characteristics that distinguish one insect order from another. When you see a new insect, start by looking closely at the characteristics listed above, especially the wings, antennae, and mouthparts.
Learn to look at these three things, and you're well on your way to identifying many kinds of insects. The images below are intended to help you learn to recognize these characteristics. Later, on a test, you will be asked to look at some insect specimens, recognize what order they're in, and understand what characteristics identify them as belonging to that order. To get started, look at the following pages on the insect orders you'll see in lab:
- Coleoptera: beetles.
- Dermaptera: earwigs.
- Diptera: flies.
- Hemiptera: true bugs.
- Hymenoptera: ants and wasps.
- Lepidoptera: butterfies and moths.
- Odonata: dragonflies.
- Orthoptera: Grasshoppers and crickets.
BugGuide, a good reference for identifying insects.
Insect Morphology in Wikipedia.
Insect Mouthparts in Wikipedia.
This page updated November 13, 2012