An insect's skeleton is on the outside of its body,
and forms a hard protective shell. This "exoskeleton" is made out of a tough, solid substance called chitin, which is both strong and
lightweight. Each insect's exoskeleton can contain chitin of different forms. Some is very rigid, and forms thick, solid structures and sharp
cutting edges of claws or mandibles*. In other areas, the chitin can be thin and flexible. The huge variety in insect forms shows that chitin
can be made into a limitless variety of shapes. There is, however, an upper limit on the size of an insect: past a certain size, the
exoskeleton simply can't provide enough support, without being so thick that no room would remain for internal organs!
Below: A dragonfly. Below left: Portrait of a grasshopper. Photos by Maya Walters
The first winged insects lived over 300 million years ago and some looked very similar to today's dragonflies -- only much larger! The oldest known fossilized dragonfly had a wingspan of 20 cm (8 in), and the largest fossilized dragonfly was found in the United States, with a wingspan of 60 cm (24 in)!
The smallest insects are even smaller than some single-celled organisms. The largest known insect is South America's Hercules beetle (Dynastes hercules), which is over twice as heavy as a mouse.
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