Detail of the surface of a spider egg. Coloured scanning electron micrograph ( SEM). The purpose of the small round structures is unclear but may aid in sticking the egg cluster together. The female spider lays thousands of eggs in one or more egg sacs made of silk and uses stored semen to fertilize them one by one. She then carries the sac on her spinnerets or attaches it to a plant or hides it to protect the eggs from predators. The spiderlings go through all the larval stages when inside the sacs and it takes a few weeks for them to hatch.Spiderlings grow through molting process before they fully become adults. Generally, they have to go through at least 5-10 molts before reaching adulthood. When they reach adulthood, the cycle starts all over again with the offspring's now mating and reproducing. Magnification: x2000 when printed at 10 centimetres wide.