1.7 General science  (Page 3/4)

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13. Make a drawing of the insect as seen from the side.

Build

• The body consists of three main parts: the head, the thorax and the abdomen.
• The insect has an exoskeleton that consists of a strong leathery material called chitin .
• The three pairs of articulated legs are attached to the thorax.
• Two pairs of wings are also attached to the thorax: the front ones are leathery and lie flat against the body; the hind ones are soft and fold underneath the front ones like fans.
• The head bears:

- two antennae (feelers) with which the insect feels;

- three small eyes that are called simple eyes;

- two large or compound eyes; and

- mouth parts.

• The abdomen has no attachments, except for small sexual organs at the tip that differ in the case of the male and the female.
• There is a small spiracle (breathing opening) on each segment of the abdomen.

Movement

Insects are very mobile. Just think about the agility of a fly and the distance that swarms of grasshoppers can fly.

The legs are articulated. The hind legs of the grasshopper are developed more strongly so that it can jump.

The front wings fold open diagonally and balance the insect during flight (like the wings of an aeroplane), while the soft hind wings fold open like fans and do the actual flying.

Feeding

The grasshopper is a herbivore with mouthparts that are very well adapted for this purpose. Amongst others, there are two small feelers with which it can feel the food so that it can push the food into its mouth. There are also two jaws with cutting edges that finely cut up the plant material. The grasshopper therefore has biting mouthparts.

Other insects have the same mouthparts as the grasshopper, although the shape can differ greatly to adapt to other ways of eating. For example, they can be licking (the fly), sucking (some moths) or biting (the mosquito).

Respiration

On either side of each of the first eight abdominal segments is a spiracle. These openings lead to a network of tubes (trachea) that branch throughout the whole body and transport air.

Maintaining a water balance

The exoskeleton of the grasshopper forms a watertight skin covering. This means that the body does not lose moisture and therefore can survive in dry conditions. The plant material eaten by the grasshopper contains sufficient water.

Reproduction

In Grade 6 you learned that a fruit fly undergoes a complete change of form, or metamorphosis, from the time the egg hatches until an adult fly has developed. Can you still remember the stages? Fill them in on the illustration below.

The grasshopper does not undergo a complete metamorphosis. After the male and female have mated, the female lays eggs in the ground with her ovipositor. The small grasshoppers that hatch look just like the adults. They moult a few times as they grow. We therefore speak of incomplete metamorphosis.