辅助记忆

millipede  milli 千，千分之一 + ped 足 + e → 千足虫

centipede centi 百 + ped 脚，足 + e → 百脚虫 → 蜈蚣

insecta in 向内 + sect 分割 + a → 节肢动物→  昆虫纲

antennae ant蚂蚁 + ennae →蚂蚁一样的线 →触角

metamorphosis meta在...之后，超出+ morphosis 形态 → 超出正常形态 →变态

以下内容来自https://www.thoughtco.com/what-are-insects-1968416仅供同学学习使用，若有侵权，请告知删除

Science, Tech, Math › Animals & Nature

What Are Insects?

Classifying and Identifying Insects

Debbie Hadley  (Entomology Expert B.A., Political Science, Rutgers University.Debbie Hadley is a science educator with 25 years of experience who has written on science topics for over a decade.)

Insects are the largest group in the animal kingdom. Scientists estimate there are over 1 million insect species on the planet, living in every conceivable environment from volcanoes to glaciers.

How Insects Are Classified

Insects are arthropods. All animals in the phylum Arthropoda have hard external skeletons called exoskeletons, segmented bodies, and at least three pairs of legs. Other classes that belong to the phylum Arthropoda include:

• Arachnida (spiders)

• Diplopoda (millipedes)

• Chilopoda (centipedes)

• 
  

• The class Insecta encompasses all of the insects on the earth. It is most often divided into 29 orders. These 29 orders use the physical characteristics of the insects to group similar insect families.

• Some insect taxonomists organize the insects differently, using evolutionary links instead of physical traits. For the purpose of identifying an insect, it makes more sense to use the system of 29 orders, since you can see the physical similarities and differences between insects you observe.

• Here is an example of how an insect, the monarch butterfly, is classified:

• Kingdom Animalia: the animal kingdom

• Phylum Arthropoda: arthropods

• Class Insects: insects

• Order Lepidoptera: butterflies and moths

• Family Nymphalidae: brush-footed butterflies

• Genus Danaus

• Species plexippus

• 
  

• The genus and species names are always italicized and used together to give the scientific name of the individual species. An insect species may occur in many regions and may have different common names in other languages and cultures.

• The scientific name is a standard name that is used by entomologists around the world. This system of using two names (genus and species) is called binomial nomenclature.

• Basic Insect Anatomy

• 
  

• As you may remember from elementary school, the most basic definition of an insect is an organism with three pairs of legs and three body regions: head, thorax, and abdomen.

• Entomologists, scientists who study insects, might also add that insects have a pair of antennae and external mouthparts. As you learn more about insects, you will find there are some exceptions to these rules.

• The Head Region

• The head region is at the front of the insect’s body and contains the mouthparts, antennae, and eyes.

• Insects have mouthparts designed to help them feed on different things. Some insects drink nectar and have mouthparts modified into a tube called a proboscis to suck up liquid. Other insects have chewing mouthparts and eat leaves or other plant matter. Some insects bite or pinch, and others pierce and suck blood or plant fluids.

• The pair of antennae may have obvious segments or look like a feather. They come in different forms and are a clue to identifying the insect. Antennae are used to perceive sounds, vibrations, and other environmental factors.

• Insects can have two types of eyes: compound or simple. Compound eyes are usually large with many lenses, giving the insect a complex image of its surroundings. A simple eye contains just a single lens. Some insects have both kinds of eyes.

• The Thorax Region

• The thorax, or middle region of an insect’s body, includes the wings and legs. All six legs are attached to the thorax. The thorax also contains the muscles that control movement.

• All insect legs have five parts. Legs can be different shapes and have different adaptations to help the insect move within its unique habitat. Grasshoppers have legs designed for jumping, while honey bees have legs with special baskets to hold pollen as the bee moves from flower to flower.

• Wings also come in different shapes and sizes and are another important clue to help you identify an insect. Butterflies and moths have wings made of overlapping scales, often in brilliant colors. Some insect wings appear transparent, with just a web of veins to identify their shape. When at rest, insects like beetles and praying mantids keep their wings folded flat against their bodies. Other insects hold their wings vertically, like butterflies and damselflies.

  The Abdomen Region

• The abdomen is the final region in the insect body and contains the insect’s vital organs. Insects have digestive organs, including a stomach and intestines, to absorb nutrients from their food and separate waste matter. The sexual organs of the insect are also in the abdomen. Glands that secrete pheromones for marking the insect’s trail or attracting a mate are in this region as well.

• Take a Closer Look

• The next time you observe a lady beetle or a moth in your yard, stop and take a closer look. See if you can distinguish the head, thorax, and abdomen. Look at the shape of the antennae, and watch how the insect holds its wings. These clues will help you identify a mystery insect, and provide information about how the insect lives, feeds and moves.

以下内容来自https://www.thoughtco.com/simple-questions-to-help-identify-an-insect-1968418仅供同学学习使用

10 Ways to Identify an Insect

By Debbie Hadley

Updated on September 27, 2019

When you encounter a new insect in your backyard, you want to know what it’s likely to do while it’s there. Is it going to eat one of your garden plants? Is it a good pollinator for your flowers? Will it lay eggs in the soil or pupate somewhere? You can learn some things about an insect just by observing it for a while, of course, but that’s not always practical. A good field guide or website may provide information about the mysterious visitor, but you need to know what it is first.

So how do you identify an insect you have never seen before? You collect as much information as you can, looking for clues that will place the insect in a taxonomic order. If you have a camera with you or a smartphone with a camera, it's a good idea to take several photos of the insect using the macro (close-up) setting. Then, ask yourself each of the following questions about your unidentified insect. You might not be able to answer all of them, but any information you gather will help narrow down the possibilities. First, be sure you are looking at an insect and not another arthropod cousin. 

01 of 10 Is It an Insect?

To be sure you're really looking at an insect, ask yourself these four questions:

1. Does it have six legs? All insects do.

2. Are there three distinct body regions—head, thorax, and abdomen? If not, it's not a true insect.

3. Do you see a pair of antennae? Antennae are a necessary insect feature.

4. Does it have a pair of wings? Most but not all insects have two pairs of wings.

02 of 10 Is the Insect an Adult?

The taxonomic orders are based on the adult forms of insects. If you have a caterpillar, for example, you won’t be able to use most guides or dichotomous keys. There are ways to identify immature insects, but for this article, we are only looking at adults.

03 of 10 Where Does It Live, and When Is It Active?

Insects live in certain types of climates and habitats. For example, many insects decompose plant matter and are typically found in soil, leaf litter, or in rotting logs. Tropical regions of the world have many unique species of butterflies and moths that you will not find in a temperate zone. Make a few notes about where you found or observed the insect.

Does the insect prefer specific plants? Some insects have important relationships with specific plants, so the plants in the area might be clues as well. A wood borer is often named for the tree it inhabits and feeds on—knowing the name of the tree can lead you to quick identification of the insect.

When is the insect most energetic? Like other animals, insects may be diurnal or nocturnal, or a combination of both. Butterflies require the sun’s warmth to fly, and so are active during the day.

04 of 10 What Do the Wings Look Like?

The presence and structure of the wings may be your best clue to identifying an insect. In fact, many insect orders are named for a specific wing characteristic. The order Lepidoptera, for example, means “scaly wings.” If you plan to use a dichotomous key to identify the insect, you will need information about the wings to complete the key.

Here are some details to observe:

• Does the insect have wings, and if so, are they well developed?

• Do you see one or two pairs of wings?

• Do the forewings and hindwings look similar or different?

• Are the wings leathery, hairy, membranous, or covered in scales?

• Can you see veins in the wings?

• Do the wings appear to be larger than the body or about the same size as the thorax?

• How does the insect hold its wings when resting—folded flat against the body or vertically above the body?

05 of 10 What Do the Antennae Look Like?

Insect antennae come in a variety of forms and are an important characteristic to examine when trying to identify an insect. If the antennae are not clearly visible, use a hand lens to get a better look, or if you've taken a photo, bump up the image on your phone or computer. Do the antennae appear threadlike or are they club-shaped? Do they have an elbow or bend? Are they feathery or bristled?

06 of 10 What Do the Legs Look Like?

An insect’s legs are adaptations that help it move, eat, and survive predators. Aquatic insects sometimes have legs that look like boat oars, and as you might expect, these legs are made for swimming. Terrestrial insects like ants spend most of their time walking and have legs designed for quick movement on the ground. Look at a grasshopper’s legs. The third pair is folded and much larger than the others. These powerful legs propel the grasshopper through the air and away from predators. Some insects are predators themselves and have front legs designed for catching and grasping smaller insects.

07 of 10 What Do the Mouthparts Look Like?

The insect world is diverse, and that diversity is well represented by their various types of mouthparts. There are insects that eat leaves, some that chew on wood, others that drink sap or nectar, and even some that prey on other insects.

Is the mouth designed for chewing, piercing, or just drinking? Many flies feed on sugary foods and have a spongelike mouth for collecting sweet fluids. Butterflies drink nectar and have a coiled tube called a proboscis, which uncurls to reach into flowers. Insects that feed on plant matter have chewing mouthparts, designed to break down plant fibers. Predatory insects, such as mantids, also have chewing mouthparts. Some insects, like weevils and aphids, specialize in drinking plant fluids. They have mouthparts that pierce the plant and then suck the fluids from inside.

If you can, use a hand lens or camera to get a closer look at the insect's mouthparts.

08 of 10 What Does the Abdomen Look Like?

The abdomen is the third region of the insect body. Like all arthropods, insects have segmented bodies. The number of abdominal segments can vary between insect orders. The abdomen may also have appendages that are clues to the identity of the mystery insect.

Does the insect have abdominal segments? The number of abdominal segments varies from six to 11. For example, silverfish usually have 11 segments. If they are visible, try counting the segments.

Does the insect have appendages at the end of the abdomen? Your mystery insect may have an obvious “tail” at the end of the abdomen or what appears to be a set of pincers. These structures are touch organs called cerci that help the insect feel. Earwigs have modified cerci that function as forceps. Three-pronged bristletails are named for their three cerci.

What is the size and shape of the insect's abdomen? Is the abdomen long and slender like a mayfly's? Does it look swollen compared to the thorax? Some identification keys use these characteristics.

09 of 10 What Color Is the Insect?

Insects can be quite colorful, with distinct markings that are unique to a certain species.

Are there colors and patterns on the insect wings? You cannot identify a butterfly without knowing the colors and patterns on its wings. Some beetles have iridescent forewings and others have spots or stripes. But it’s not just insect wings that come in every color of the rainbow. Their bodies may also have unique and colorful markings. Monarch butterflies are known for their orange and black wings, but many people don’t notice the white polka dots on their black bodies.

Are there patterns on the insect's body? Note any colors and patterns on the wings and the body of your mystery insect. If there are dots or stripes, try to count them. Some species mimic the colors of others as a means of fooling predators, so your observations need to be as specific as possible.

10 of 10 How Does It Move?

It's helpful to note how your mystery insect moves, whether in captivity or in the wild.

Does the insect fly, jump, walk, or wriggle? If you observe the insect flying, you know it is a winged insect and can eliminate at least four insect orders (the wingless insects) from your guesses. Some insects, like grasshoppers, prefer to propel themselves with their legs but are capable of flying when necessary. Mantids walk unless threatened, and then they will fly as well. Even if these traits don’t give you definitive answers to an insect’s identity, making notes on their movement patterns will teach you something about how that insect lives.