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Horticulture Principles and Practices

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FIGURE 7–1 Life cycle of an<br />

insect with no metamorphosis.<br />

Egg<br />

Adult<br />

Young<br />

Young<br />

FIGURE 7–2 Life cycle of an insect<br />

with gradual metamorphosis.<br />

Egg<br />

Adult<br />

Nymph<br />

Nymph<br />

4. Complete metamorphosis. A complete metamorphosis consists of four distinct<br />

stages, in none of which the insect looks like the adult (Figure 7–4). The egg<br />

hatches into a larva that feeds on plant foliage <strong>and</strong> other parts. The larva passes<br />

through a dormant stage called pupa. The mature adult emerges from the pupa as<br />

a beautiful butterfly, which is harmless to plants. Examples of insects in this<br />

class are Lepidoptera (butterflies) <strong>and</strong> Hymenoptera (bees). Bees <strong>and</strong> butterflies<br />

are important in aiding crop pollination. The larvae differ from one order to<br />

another. In Diptera (flies), the larva is called a maggot. The larvae of Lepidoptera<br />

(butterflies <strong>and</strong> moths) are called caterpillars (Figure 7–5). Certain larvae tunnel<br />

through leaves, as occurs in the Diptera orders; they are called miners. Larvae of<br />

moths <strong>and</strong> beetles are able to tunnel through stems <strong>and</strong> other tissue <strong>and</strong> are called<br />

borers.<br />

224 Chapter 7 Biological Enemies of Horticultural Plants

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