Insects develop from birth to maturity in stages called life cycles. Unlike humans, insects have a hard outer shell called an exoskeleton. As they grow, they have to shed the tough outer skin. Depending on the type of insect, this will occur a number of times throughout the life cycle until they reach adulthood. Below is a detailed description of the two life cycles among insects: simple development and complex development.
Birth
Most insects begin life as an egg. When an insect has developed fully, the insect inside of the egg will break out of the shell by chewing the covering or expanding and contracting its muscles to break the shell. This usually happens seven to 10 days after the egg is laid. These insects then progress through the life cycle stages, often ending up looking far different than they did at birth. Some insects start life, like humans, through an active birth. The live young usually resemble their adult counterparts, just in a smaller form and without reproductive organs.
Nymph
The nymph stage is the second part of the simple development life cycle. It is called simple because these insects are born looking just as they do as adults, only smaller. Molting is still a part of this process. Insects who undergo simple development include grasshoppers and cockroaches. Winged insects that are part of this group, like dragonflies, do not undergo the pupa stage in which most winged insects develop their wings. Instead, these types of insects, known as apterygote, develop increasingly larger wings through each molting process during the nymph stage.
Larvae
The larvae stage is the second part of the complex developmental life cycle. Insects that undergo a dramatic transformation from birth until they reach adulthood develop partially during the larvae process. They always appears like worms or small caterpillars. The shedding of the exoskeleton during the larvae stage occurs from three to six times, with the insects growing larger each time. The period in between the stages of molting during the larvae phase is known as an instar. During this phase, insects grow until they are large enough that they outgrow their skin and molt.
Pupae
Winged insects that undergo the larvae stage, progress to the pupae stage for final development into adulthood. Only small, gradual changes occur during the larvae stage, but the pupae stage involves major changes. Because of this, it is often known as metamorphosis. The pupae stage involves the insects wrapping themselves into cocoons where they develop slowly over time. When the insects emerge from the cocoons, they look completely differently from what they looked like during the larvae stages, and the pupae are complete.
Adulthood
After the nymph stage (for insects with simple life cycles), larvae and pupae stage (for insects with complex life cycles), the final stage of the life cycle is adulthood. During adulthood, the insects are fully developed. Ironically, the developmental stages of the life cycle sometimes last longer than adulthood itself. For instance, cicadas spend 17 years in the larvae and pupae phases, and just a few weeks as adults.
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