CK12 Life Science

Table 12.7:

Type of Metamor-

phosis

None Incomplete Complete

Characteristics Only difference be-

tween adult and lar-

vae is size

Young, called

nymphs (Figure

12.36), usually sim-

ilar to adult, wings

then appear as buds

on nymphs or early

forms; when last

molt is completed

wings expand to full

adult size

Insects have dif-

ferent forms in

immature and adult

stages, have dif-

ferent behaviors,

and live in different

habitats; immature

form is called larvae

and remains similar

in form but increases

in size; they usu-

ally have chewing

mouthparts even if

adult mouthparts

are sucking ones; at

last larval stage of

development insect

forms into pupa

(Figure 12.37),

doesn’t feed and

is inactive; here

wing development is

initiated, and adult

emerges

Example Silverfish Dragonflies Butterflies and

Moths

Importance of Insects

Many insects are considered to be pests by humans. In spite of this, insects are also very
important. In the environment, some insects pollinate flowering plants, as in wasps, bees,
butterflies, and ants. Many insects, especially beetles, are scavengers, feeding on dead ani-
mals and fallen trees, and insects are responsible for much of the process by which topsoil is
created.

Insects also produce useful substances as honey, wax, lacquer, and silk. Honeybees have
been cultured by humans for thousands of years for honey. The silkworm has greatly affected