Body Shape & Structure Change in Arthropods

Complex Life Cycles

• Compared to mammals, most arthropods have complex life cycles. Some hatch from their eggs looking like miniature adults. Others have nymph or larval forms that differ those of adults.

Incomplete Metamorphosis

• Incomplete metamorphosis means that an insect does not go through the pupal stage. This type of metamorphosis has only three stages, embryo, nymph and adult. Nymphs look like miniature adults, but they lack wings. As they grow, their old exoskeletons split open, revealing a soft, new body that will harden over time. Grasshoppers, dragonflies and damselflies are examples of insects that go through incomplete metamorphosis.

Complete Metamorphosis: Larvae

• Insects that undergo complete physical change go through complete metamorphosis. They begin life as embryos and are called larvae after hatching. Larvae, like maggots and caterpillars, are worm-like and spend their time eating and growing.

Complete Metamorphosis: Pupa

• The pupal stage precedes the adult stage and is characterized by inactivity. As a butterfly changes from caterpillar to chrysalis, its larval body actually splits open, revealing the chrysalis inside.

Crustaceans

• Crustacean life cycles are not as simple as those of insects. Lobsters and crabs, for example, hatch larvae that look nothing like adults, but must molt from zoeae to magalops and then finally into tiny adults. A barnacle, on the other hand, must go through several complex stages before attaching to a solid surface and becoming an adult.