The Life Cycle of a Spider

All spiders, from the tiniest jumping spider to the largest tarantula, have the same general life cycle. They mature in three stages: egg, spiderling, and adult. Though the details of each stage vary from one species to another, they are all very similar.

The spider mating ritual also varies and males must approach a female carefully or he may be mistaken for prey. Even after mating, many male spiders will die though the female is very independent and will care for her eggs on her own. Despite the rumors, the majority of female spiders do not eat their mates.

Egg, the Embryonic Stage

After mating, female spiders store sperm until they are ready to produce eggs. The mother spider first constructs an egg sac from strong silk that is tough enough to protect her developing offspring from the elements. She then deposits her eggs inside it, fertilizing them as they emerge. A single egg sac may contain just a few eggs, or several hundred, depending on the species.

Spider eggs generally take a few weeks to hatch. Some spiders in temperate regions will overwinter in the egg sac and emerge in spring. In many spider species, the mother guards the egg sac from predators until the young hatch. Other species will place the sac in a secure location and leave the eggs to their own fate.

Wolf spider mothers carry the egg sac with them. When they're ready to hatch, they will bite the sac open and free the spiderlings. Also unique to this species, the young spend as many as ten days hanging onto their mother's back.

Spiderling, the Immature Stage

Immature spiders, called spiderlings, resemble their parents but are considerably smaller when they first hatch from the egg sac. They immediately disperse, some by walking and others by a behavior called ballooning.

Spiderlings that disperse by ballooning will climb onto a twig or other projecting object and raise their abdomens. They release threads of silk from their spinnerets, letting the silk catch the wind and carry them away. While most spiderlings travel short distances this way, some can be carried to remarkable heights and across long distances. 

The spiderlings will molt repeatedly as they grow larger and they're very vulnerable until the new exoskeleton forms completely. Most species reach adulthood after five to 10 molts. In some species, the male spiders will be fully mature as they exit the sac. Female spiders are always larger than males, so often take more time to mature.

Adult, the Sexually Mature Stage

When the spider reaches adulthood, it is ready to mate and begin the life cycle all over again. In general, female spiders live longer than males; males often die after mating. Spiders usually live just one to two years, though this does vary by species.

Tarantulas have unusually long life spans. Some female tarantulas live 20 years or more. Tarantulas also continue molting after reaching adulthood. If the female tarantula molts after mating, she will need to mate again, because she sheds the sperm storage structure along with her exoskeleton.

Resources and Further Reading

• Cranshaw, Whitney, and Richard Redak. Bugs Rule!: An Introduction to the World of Insects. Princeton University, 2013.
• Evans, Arthur V. National Wildlife Federation: Field Guide to Insects and Spiders of North America. Sterling, 2007.
• Savransky, Nina, and Jennifer Suhd-Brondstatter. “Spiders: An Electronic Field Guide.” Field Biology, Brandeis University, 2006.