Egg sac to adult
Spider eggs develop and hatch within the egg sac, the larval spider undergoing at least one further moult before emerging from the sac. The number of growth moults varies between species, as well as with size and nutritional state. Poorly fed spiders will moult fewer times and become smaller adults. Most spiders undergo 5-10 moults to reach adulthood. Males often have fewer and faster moults. Extreme examples of this are given by the Magnificent spider (Ordgarius magnificus) and the Bird Dung spider (Calaenia kinbergi), both large, specialised moth catching relatives of the orb weavers. The males moult only within the egg sac, emerging as tiny, fully mature males along with their similarly sized and very immature sisters, which will take many weeks and moults to become large adult females.
A spider's appearance can change considerably during growth from spiderling to adult, as indicated by these stages in Redback Spider development. Adult males and females also may look quite different, especially in respect of size and colour. Spiders with good eyesight like jumping spiders often have colourful or strikingly marked males which differ considerably from their drabber females.
