Invertebrates

Figure 33.15

Table 33.5

ORDER Blattodea 4,000 Cockroaches have a dorsoventrally flattened body, with legs modified for rapid running. Forewings, when present, are leathery, whereas hind wings are fanlike. Fewer than 40 cock- roach species live in houses; the rest exploit habitats ranging from tropical forest floors to caves and deserts. Beetles comprise the most species-rich order of insects. They have two pairs of wings, one of which is thick and leathery, the other membranous. They have an armored exoskeleton and mouthparts adapted for biting and chewing. Beetles undergo complete metamorphosis. Earwigs are generally nocturnal scavengers. While some species are wingless, others have two pairs of wings, one of which is thick and leathery, the other membranous. Earwigs have biting mouthparts and large posterior pincers. They un- dergo incomplete metamorphosis. Dipterans have one pair of wings; the second pair has become modified into balancing organs called halteres. Their head is large and mobile; their mouthparts are adapted for sucking, piercing, or lapping. Dipterans undergo complete metamorpho- sis. Flies and mosquitoes are among the best-known dipterans, which live as scavengers, predators, and parasites. Hemipterans are so-called “true bugs,” including bed bugs, assassin bugs, and chinch bugs. (Insects in other orders are sometimes erroneously called bugs.) Hemipterans have two pairs of wings, one pair partly leathery, the other membranous. They have piercing or sucking mouthparts and undergo incomplete metamorphosis. Ants, bees, and wasps are generally highly social insects. They have two pairs of membranous wings, a mobile head, and chewing or sucking mouthparts. The females of many species have a posterior stinging organ. Hymenopterans undergo com- plete metamorphosis. Termites are widespread social insects that produce enormous colonies. It has been estimated that there are 700 kg of termites for every person on Earth! Some termites have two pairs of membranous wings, while others are wingless. They feed on wood with the aid of microbial symbionts carried in specialized chambers in their hindgut. Coleoptera 350,000 Dermaptera 1,200 Diptera 151,000 Hemiptera 85,000 Hymenoptera 125,000 Isoptera 2,000 APPROXIMATE NUMBER OF SPECIES MAIN CHARACTERISTICSEXAMPLES German cockroach Japanese beetle Earwig Horsefly Leaf- Footed bug Cicada-killer wasp Termite Figure 33.37

Lepidoptera 120,000 Butterflies and moths are among the best-known insects. They have two pairs of wings covered with tiny scales. To feed, they uncoil a long proboscis. Most feed on nectar, but some species feed on other substances, including animal blood or tears. Odonata 5,000 Dragonflies and damselflies have two pairs of large, membran- ous wings. They have an elongated abdomen, large, compound eyes, and chewing mouthparts. They undergo incomplete meta- morphosis and are active predators. Orthoptera13,000 Grasshoppers, crickets, and their relatives are mostly herbi- vorous. They have large hind legs adapted for jumping, two pairs of wings (one leathery, one membranous), and biting or chewing mouthparts. Males commonly make courtship sounds by rubbing together body parts, such as a ridge on their hind leg. Orthopterans undergo incomplete metamorphosis. Phasmida2,600 Stick insects and leaf insects are exquisite mimics of plants. The eggs of some species even mimic seeds of the plants on which the Insects live. Their body is cylindrical or flattened dorsoventrally. They lack forewings but have fanlike hind wings. Their mouthparts are adapted for biting or chewing. Phthiraptera 2,400 Commonly called sucking lice, these insects spend their entire life as an ectoparasite feeding on the hair or feathers of a single host. Their legs, equipped with clawlike tarsi, are adapted for clinging to their hosts. They lack wings and have reduced eyes. Sucking lice undergo incomplete metamorphosis. Siphonaptera2,400 Fleas are bloodsucking ectoparasites on birds and mammals. Their body is wingless and laterally compressed. Their legs are modified for clinging to their hosts and for long-distance jumping. They undergo complete metamorphosis. Thysanura 450 Silverfish are small, wingless insects with a flattened body and reduced eyes. They live in leaf litter or under bark. They can also infest buildings, where they can become pests. Trichoptera 7,100 The larvae of caddisflies live in streams, where they make houses from sand grains, wood fragments, or other material held to- gether by silk. Adults have two pairs of hairy wings and chewing or lapping mouthparts. They undergo complete metamorphosis. Swallowtail butterfly Dragonfly Katydid Stick insect Human Body louse Flea Silverfish Caddisfly ORDER APPROXIMATE NUMBER OF SPECIES MAIN CHARACTERISTICS EXAMPLE Figure 33.37