It is a barrier to water loss and can support a body deprived of water's buoyancy. Appendages became specialized for feeding, sensing, locomotion, sperm transfer, and spinning silk. In some lineages this has resulted in a head, thorax, and abdomen regions. This allows high metabolic rates and sustained activity, as in flight. Many individual units of the eye allow motion perception.
Larval stages concentrate on feeding and growth.
Adults specialize in dispersal and reproduction. The process of change from larva to adult is called metamorphosis. A Look at Spiders and Their Kin Chelicerates include some marine species such as horseshoe crabs and more familiar arachnids. Arachnids include spiders, scorpions, ticks, and mites. Spiders are keen predators that trap insects in their webs produced as silk strands from the abdomen.