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Background
Arthropods follow varied life cycles depending on their group, but in general, their life begins as eggs which undergo a certain incubation period. Generally, the eggs are laid outside the mother's body. Most arthropod parents supervise their eggs. However, when these eggs hatch, the offspring are usually left to develop on their own. Life cycles of arthropods vary with the major subgroups These include Arachnida (spiders, mites and scorpions), Crustacea (lobsters, crabs and shrimps), Insecta (insects) and Diplopoda (millipedes and centipedes). These groups follow slightly different patterns of development.
Molting
Molting plays an important role in the growth and development of all groups of arthropods. The tough exoskeleton of arthropods does not grow, so they have to conduct the process of molting--shredding the exoskeleton to facilitate the growth of the animal. Molting is controlled by the arthropod's hormones. Molting starts by secreting an inner layer of tissue. The arthropods will slowly pull out from the exoskeleton and will remain vulnerable for a certain period of time until the new exoskeleton is fortified. Generally, molting's frequency decreases as arthropods reach the adult stage. The time in between molts is called the intermolt interval.
Crustaceans
Some arthropods, especially those belonging to the subgroup of crustaceans, undergo three major stages of life cycle. When they hatch, they come out in a larva form that does not have any resemblance to their adult form. They will undergo a series of molting until they become juveniles. A juvenile is a small version of the arthropod's adult appearance. Then they will undergo more molting processes until they become full adults.
Metamorphosis
A great number of insects belonging to the phylum Arthropoda undergo a developmental cycle called metamorphosis--the process where the insect goes through stages experiencing dramatic alterations in in physical makeup and needs. Complete metamorphosis consists of four cycles. These are egg or embryo, juvenile, pupa and adult. The juvenile stage can also be called larvae, nymphs or naiads depending on the type of species. In most cases, the juvenile's growth needs consecutive molting process to become a pupa. The pupa in time becomes an adult.
Incomplete Metamorphosis
In other groups of insects, life cycle is referred to as incomplete metamorphosis. In this type of life cycle, the egg hatches and become what is called a nymph or larvae. Nymphs appear to be a small adult with no wings. A nymph also goes through several moltings until it fully develops into a mature adult capable of reproduction. One significant factor that affects some insects' growth is temperature. Generally, growth rate increases at a higher temperature.