The insect body plan
The adult insect body plan has three main parts: head, thorax and abdomen. Its usual six legs attach to the thorax, and its antennae are on the head. Many adults have wings. An outer covering called an exoskeleton supports and protects the body.
What a learner can do afterwards
- Name the head, thorax and abdomen in front-to-back order and identify the thorax as the middle body part
- Describe the usual adult insect body plan as six legs attached to the thorax
- Explain that an insect's outer covering, called an exoskeleton, supports and protects its body rather than internal bones
1 · Read
You have met ants, beetles and butterflies. These are insects. An adult insect has three main body parts. The head is at the front. The thorax is in the middle. The abdomen is at the back.
The usual adult insect body plan has three pairs of legs, making six legs. All six attach to the thorax. Young insects can look different. An injured adult may lose or damage a leg. This does not change its animal group. To count legs on several complete adults, count six for each animal and add the groups.
Each dot stands for one leg. The three groups show three pairs, not where the legs attach.
An adult beetle has two antennae, or feelers, on its head, along with its eyes and mouth. Its legs attach to the thorax. Wings, when present, attach there too. The abdomen is behind the thorax. A list can help you remember these names, but you need a clear picture or specimen to see the actual body parts.
Insects have no internal bones. Their outer covering is called an exoskeleton. It supports and protects the body. Some parts are hard. Flexible parts let the body bend and move. The exoskeleton is outside the body, not a set of bones inside.
An adult insect has a head, thorax and abdomen. Its usual six legs attach to the thorax. Its outer exoskeleton supports and protects its body.
Original lesson, questions and flashcards written for this learning dataset.
Reading text written for this learning dataset. Linked videos are by TED-Ed and SciShow Kids (Complexly).
More to read
Locate the parts
Use a clear picture of an adult beetle to practise three names.
Find the front end first. That is the head, where the antennae are. Follow the body back to the thorax. The legs join this middle part. Behind it is the abdomen.
Try pointing to each part while saying its name. Word boxes can help you remember the order, but they do not show the insect's shape or where its legs join.
Legs in groups
Three pairs of legs are part of the usual adult insect body plan. A pair has two, so the pairs make six legs.
You may not always see six on a living animal. A leg may be hidden or missing. Young insects can also look different from adults.
If a counting question gives several complete adults, keep a separate group of six for each animal. Add the groups to find the total.
Support on the outside
Your bones are inside your body. A beetle has no internal bones. Its supporting covering is outside.
That covering is an exoskeleton. It protects the beetle as well as supporting its body. It has hard parts and flexible parts. Flexible areas allow bending and movement.
When you hear exoskeleton, think about the position of the covering: outside the body.
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Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.