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Korea Biodiversity Information System > Insect Resource > Insect Classes > Insect Structure

Insect Structure

Insect structure

External morphology of insects

Segmented composition is the biggest characteristic of insects, and the skin between segments is soft and folded inward in a membranous form. Insect body segments are divided into four sections, tergum, sternum, and laterotergites, and their bodies are divided into head, thorax and abdomen.

Thorax

The thorax is composed of three sections: prothorax, mesothorax, and metathorax, each of which has one pair of legs. Also, the mesothorax and metathorax each have one pair of wings. Therefore, the muscles of the thorax are more developed than any other part of the insect body. Their legs are composed of five segments: coxa, trochanter, femur, tibia, and tarsus.

Abdomen

Insect abdomens are connected to the metathorax, and normally composed of 10 or 11 segments. There are some cases where some front and posterior segments are atrophied or transformed to show a smaller number of external segments. In some cases, the posterior abdomen has two or three caudal legs, and the female often has an ovipositor.

Head

In general, insect heads have one pair of antennae, three ocelli and compound eyes, a mandible, a maxilla, and a lower lip.

Insect characteristics

Insect is a large group of more than 850,000 species and accounts for at least 3/4 of the entire animal kingdom. They have various morphological characteristics, which are organized as follows.

• The body is divided into head, thorax, and abdomen, and the head has one pair of antennae and specifically developed gnathal segment.
• Insects differ from other animals in having an exoskeleton.
• Insect abdomens are composed of 11 segments during the larva stage, and the appendage disappears when the insect becomes an imago.
• The body is bisymmetric.
• Insects have an open circulatory system.
• Their digestive system is composed of three parts: foregut, mid-gut, and hindgut, and there is a malpighian tubule at the end of hindgut.
• They breathe through their trachea and spiracle.
• In general, males and females are separated.