Invertebrates
Figure 33.15
Table 33.5
ORDER
Blattodea
Coleoptera
Dermaptera
Diptera
Hemiptera
Hymenoptera
APPROXIMATE
NUMBER OF
SPECIES
4,000
350,000
MAIN CHARACTERISTICS
EXAMPLES
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 cockroach species live in houses; the rest exploit habitats ranging
from tropical forest floors to caves and deserts.
German
cockroach
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.
Japanese
beetle
1,200
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 undergo incomplete metamorphosis.
Earwig
151,000
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 metamorphosis. Flies and mosquitoes are among the best-known dipterans,
which live as scavengers, predators, and parasites.
85,000
125,000
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.
Horsefly
LeafFooted
bug
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 complete metamorphosis.
Cicada-killer wasp
Isoptera
Figure 33.37
2,000
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.
Termite
ORDER
Lepidoptera
APPROXIMATE
NUMBER OF
SPECIES
120,000
5,000
Odonata
EXAMPLE
MAIN CHARACTERISTICS
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.
Swallowtail
butterfly
Dragonflies and damselflies have two pairs of large, membranous wings. They have an elongated abdomen, large, compound
eyes, and chewing mouthparts. They undergo incomplete metamorphosis and are active predators.
Dragonfly
Orthoptera
13,000
Grasshoppers, crickets, and their relatives are mostly herbivorous. 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.
Katydid
Phasmida
Phthiraptera
Siphonaptera
2,600
2,400
2,400
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.
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.
Stick insect
Human
Body
louse
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.
Flea
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.
Silverfish
Trichoptera
Figure 33.37
7,100
The larvae of caddisflies live in streams, where they make houses
from sand grains, wood fragments, or other material held together by silk. Adults have two pairs of hairy wings and chewing
or lapping mouthparts. They undergo complete metamorphosis.
Caddisfly