Arthropods are the largest group of animals on Earth. This post explains the definition, classification, and characteristics of arthropods, while helping English learners expand their vocabulary with real examples.
Arthropods include chelicerates, crustaceans, hexapods, myriapods, and extinct trilobites. Learning about these animals can help you improve both your scientific knowledge and your English vocabulary.
What Are Arthropods?
Related Links: Invertebrates Vocabulary | Animals Vocabulary
Arthropods are invertebrate animals that have jointed legs, segmented bodies, and an external skeleton called an exoskeleton.
The exoskeleton is made mainly of chitin. It protects the body but does not grow with the animal.
Because the exoskeleton cannot expand, arthropods must periodically shed it in a process called molting. After molting, a new and larger exoskeleton forms.
Arthropods represent over 80% of all known animal species. They live in nearly every habitat on Earth including forests, deserts, oceans, and freshwater environments.
Scientific note: Arthropods have an open circulatory system with fluid called hemolymph, not blood like vertebrates.
Comprehensive List of Arthropods for English Learners
| Vocabulary | IPA (US) | Short Description |
|---|---|---|
| Ant | /ænt/ | Small social insect that lives in organized colonies. |
| Bee | /biː/ | Flying insect that produces honey and pollinates plants. |
| Wasp | /wɑːsp/ | Stinging insect with a narrow waist. |
| Butterfly | /ˈbʌt̬.ɚ.flaɪ/ | Colorful insect with large wings that feeds on nectar. |
| Moth | /mɔːθ/ | Insect similar to a butterfly, usually active at night. |
| Beetle | /ˈbiː.t̬əl/ | Insect with hard wing covers. |
| Ladybug | /ˈleɪ.di.bʌɡ/ | Small red beetle that eats pests. |
| Dragonfly | /ˈdræɡ.ən.flaɪ/ | Fast insect with long body and transparent wings. |
| Grasshopper | /ˈɡræsˌhɑː.pɚ/ | Jumping insect with strong hind legs. |
| Cricket | /ˈkrɪk.ɪt/ | Insect known for chirping sounds. |
| Cockroach | /ˈkɑːk.roʊ.tʃ/ | Hardy insect that survives in many environments. |
| Fly | /flaɪ/ | Insect with one pair of wings. |
| Mosquito | /məˈskiː.toʊ/ | Blood-feeding flying insect. |
| Termite | /ˈtɝː.maɪt/ | Insect that eats wood. |
| Firefly | /ˈfaɪɚ.flaɪ/ | Insect that produces light. |
| Praying mantis | /ˈpreɪ.ɪŋ ˈmæn.tɪs/ | Predatory insect with folded front legs. |
| Spider | /ˈspaɪ.dɚ/ | Arachnid with eight legs. |
| Tarantula | /təˈræn.tʃə.lə/ | Large hairy spider. |
| Scorpion | /ˈskɔːr.pi.ən/ | Arachnid with pincers and a stinger. |
| Tick | /tɪk/ | Parasitic arachnid that feeds on blood. |
| Mite | /maɪt/ | Tiny arachnid found in many environments. |
| Pseudoscorpion | /ˌsuː.doʊˈskɔːr.pi.ən/ | Arachnid without a tail or sting, resembling a scorpion. |
| Sea spider | /siː ˈspaɪ.dɚ/ | Marine arthropod from class Pycnogonida, not a true spider. |
| Horseshoe crab | /ˈhɔːrs.ʃuː kræb/ | Ancient marine chelicerate, not a true crab. |
| Crab | /kræb/ | Crustacean with a broad shell and claws. |
| Lobster | /ˈlɑːb.stɚ/ | Large crustacean with strong claws. |
| Shrimp | /ʃrɪmp/ | Small crustacean; can be singular or plural. |
| Prawn | /prɔːn/ | Crustacean similar to shrimp. |
| Krill | /krɪl/ | Tiny crustaceans important in ocean food chains. |
| Copepod | /ˈkoʊ.pə.pɑːd/ | Small planktonic crustacean with huge biomass in oceans. |
| Centipede | /ˈsen.tɪ.piːd/ | Predator with one pair of legs per segment. |
| Millipede | /ˈmɪl.ɪ.piːd/ | Slow arthropod with many legs. |
| Trilobite | /ˈtraɪ.loʊ.baɪt/ | Extinct marine arthropod fossil. |
The 5 Main Groups of Arthropods (Classification)
Related Links: Insects Vocabulary | Crustaceans Vocabulary
Chelicerates (Spiders, Scorpions, and Relatives)
Chelicerates are arthropods that possess specialized mouthparts called chelicerae. Unlike other major groups, they do not have antennae.
This group includes arachnids and unique marine arthropods like sea spiders (Pycnogonida), which are not true spiders.
- Spider
- Scorpion
- Tick
- Mite
- Harvestman
- Horseshoe crab
- Sea spider
| Vocabulary | IPA (US) | Description |
|---|---|---|
| Chelicerae | /kəˈlɪs.ə.riː/ | Feeding mouthparts of chelicerates. |
| Arachnid | /əˈræk.nɪd/ | Eight-legged arthropod. |
| Pedipalp | /ˈped.ɪ.pælp/ | Appendage used to handle prey. |
| Pycnogonida | /ˌpɪk.nəˈɡɑː.nɪ.də/ | Class of sea spiders. |
Crustaceans (Crabs, Lobsters, and Shrimp)
Crustaceans are mostly aquatic arthropods. Many have a cephalothorax.
- Crab
- Lobster
- Shrimp
- Prawn
- Krill
- Barnacle
- Copepod
| Vocabulary | IPA (US) | Description |
|---|---|---|
| Crustacean | /krʌˈsteɪ.ʃən/ | Aquatic arthropod. |
| Cephalothorax | /ˌsef.ə.loʊˈθɔːr.æks/ | Fused head and thorax. |
| Biramous limbs | /baɪˈreɪ.məs/ | Two-branched limbs. |
| Exoskeleton | /ˌek.soʊˈskel.ə.tən/ | External skeleton. |
Hexapods (Insects and Close Relatives)
Hexapods are arthropods with six legs. Most belong to Insecta, but the group also includes small non-insect relatives such as collembolans.
- Ant
- Bee
- Butterfly
- Beetle
- Mosquito
- Dragonfly
- Grasshopper
- Cockroach
| Vocabulary | IPA (US) | Description |
|---|---|---|
| Hexapod | /ˈhek.sə.pɑːd/ | Six-legged arthropod. |
| Thorax | /ˈθɔːr.æks/ | Middle body segment. |
| Abdomen | /ˈæb.də.mən/ | Rear body section. |
| Antenna | /ænˈten.ə/ | Sensory organ. |
| Collembolan | /kəˈlem.bə.lən/ | Primitive hexapod (springtail). |
Myriapods (Centipedes and Millipedes)
The word myriapod comes from Greek meaning “many feet”, not literally 10,000. Even the largest species has just over 1,000 legs.
- Centipede
- Millipede
- Pauropod
| Vocabulary | IPA (US) | Description |
|---|---|---|
| Myriapod | /ˈmɪr.i.ə.pɑːd/ | Many-legged arthropod. |
| Centipede | /ˈsen.tɪ.piːd/ | Fast predator. |
| Millipede | /ˈmɪl.ɪ.piːd/ | Slow decomposer. |
| Forcipule | /fɔːrˈsɪp.juːl/ | Venom claw. |
Trilobites (Extinct Arthropods)
Trilobites lived during the Paleozoic Era and are now extinct.
| Vocabulary | IPA (US) | Description |
|---|---|---|
| Trilobite | /ˈtraɪ.loʊ.baɪt/ | Fossil marine arthropod. |
| Fossil | /ˈfɑː.səl/ | Preserved remains. |
| Paleozoic | /ˌpeɪ.li.oʊˈzoʊ.ɪk/ | Ancient geological era. |
Arthropod Vocabulary: Facts & Clarifications
Spiders vs. Insects
- Spiders have eight legs
- Insects have six legs
- Spiders have two body segments
- Insects have three body segments
Scorpions
Scorpions use their pedipalps to grasp prey and their tail (with a sting) to inject venom.
Compound Eyes
Many arthropods such as insects and crustaceans have compound eyes.
Most spiders have simple eyes, not compound eyes.