Insect pest lifecycles

Insects of the arthropods group are the most influential in horticulture, both as pests but also as beneficial soil organisms. Arthropods can be divided into two main groups based on their lifecycle, which occur in stages called instars:

Endopterygeta (incomplete metamorphosis)

In this group the insect lays eggs (in which form they can overwinter) which hatch into nymphs, which are also known as crawlers. Nymphs ressemble adults but lack fully developed wings and sexual organs, so they have restricted mobility between plants and cannot reproduce. The nymphs can continue to have between 2 and 7 instars, each time becoming more similar to the adults, before they reach maturity. Insects in this group include aphids, thrips and earwigs.

Endopterygota (complete metamorphosis)

Insects in this group lay eggs which hatch into a larva (eg caterpillars) which differ in shape from the adult. Often this is the most destructive stage in the lifecyle from a plant’s point of view. In its second instar the insect forms a pupa (also called a chrysalis) which then hatches into the adult (sometimes after overwintering as a pupa). Insects in this group include moths, butterflies, flies, beetles and sawflies.