Insects are invertebrates, animals without backbones. They belong to a category of invertebrates called arthropods, which all have jointed legs, segmented bodies, and a hard outer covering called an exoskeleton. Two other well-known groups of arthropods are crustaceans, which include crayfish and crabs, and arachnids, which include spiders, ticks, mites, and scorpions. Many types of arthropods are commonly called bugs, but not every "bug" is an insect. Spiders, for example, are not insects, because they have eight legs and only two main body segments.
- invertebrate [inˈvə:tibrət] n.无脊椎动物
- arthropod [ˈɑ:θrəpɔd] n.节肢动物
- jointed [ˈdʒɔintid] adj.有关节的
- segmented [seɡˈmentid] adj.分段的
- exoskeleton [ˌeksəuˈskelitən] n.外骨骼
- crustacean [krʌˈsteiʃən] n.甲壳纲动物
- crayfish [ˈkrei-fiʃ] n.龙虾
- crab [kræb] n.蟹
- arachnid [əˈræknid] n.蜘蛛纲动物
- spider [ˈspaidə] n.蜘蛛
- tick [tik] n.(寄生于体大动物的吸血小虫)壁虱
- mite [mait] n.螨类
- scorpion [ˈskɔ:piən] n.蝎子
- bug [bʌɡ] n.虫子
