Chapter 21

Managing Vineyard Insect and Mite Pests

Biology of Insects

Insect Growth and Development

Most insects start life in an egg stage. The act of egg laying is called oviposition. The reproductive adult females of many species lay their eggs specifically in the area where the offspring will feed. A few insects, such as aphids, give birth to live young.

The two major categories of growth and development are simple and complete metamorphosis. Simple metamorphosis (sometimes called incomplete metamorphosis) occurs in those insect species in which the young usually look very similar to the adults, except that wings are absent and they are not reproductively mature. In the immature stage, these insects are called nymphs. Common insects that undergo simple metamorphosis include aphids, whiteflies, thrips, mealybugs, scales, grasshoppers, crickets, true bugs, and leafhoppers. Mites, which are not insects, also develop by simple metamorphosis.

Insect Feeding

Insects with simple metamorphosis often feed as both nymphs and adults in the same location and on the same food. This is true of aphids, mites, mealybugs, scales, and thrips. The larvae of insects with complete metamorphosis often feed in a different location and on a different food than the adults. For example, black vine weevil larvae feed on roots, but the adults feed on foliage. Some insects, especially those with complete metamorphosis, feed primarily in the immature stages, and adult feeding may be insignificant. For example, leafminer maggots feed by chewing on plant tissue in their mines, while the adult flies feed by sucking plant juices from holes made in the leaves.

Mites

Mites are not actually insects, but belong to the related class Arachnida, which also includes spiders, scorpions, and ticks. The major morphological differences between mites and insects are found in the number of major body parts and the number of legs. The head, thorax, and abdomen, which are separate for insects, are fused into a single continuous body region for mites and, except for the initial mite developmental stage mites have eight legs, whereas insects have six.

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