Insect Physiology - Life Cycle

Life Cycle

An insect’s life-cycle can be divided into three types:

• Ametabolous, no metamorphosis, these insects are primitively wingless where the only difference between adult and nymph is size, e.g. Order: Thysanura (Silverfish) (Triplehorn & Johnson, 2005).
• Hemimetabolous, or incomplete metamorphosis. The terrestrial young are called nymphs and aquatic young are called naiads. Insect young are usually similar to the adult. Wings appear as buds on the nymphs or early instars. When the last moult is completed the wings expand to the full adult size, e.g. Order: Odonata (Dragonflies).
• Holometabolus, or complete metamorphosis. These insects have a different form in their immature and adult stages, have different behaviours and live in different habitats. The immature form is called larvae and remains similar in form but increases in size. They usually have chewing mouthparts even if the adult form mouth parts suck. At the last larval instar phase the insect forms into a pupa, it doesn’t feed and is inactive, and here wing development is initiated, and the adult emerges e.g. Order: Lepidoptera (Butterflies and Moths), (Triplehorn & Johnson, 2005).