Spiders have 8 eyes in two rows that detect movement and locate stuff. Gas exchange is from tracheal tubes that go down into body through exoskeleton, book lungs, both. Book lungs are plates of vascularized tissue, like pages of a book. Lots of surface area for O2 and CO2 exchange. Air comes in by abdominal slits.
Silk is secreted from abdomen glands as liquid, then hardens as it leaves body.
Nests, cocoon, trap, dragline, which is also used to communicate with other spiders of same species. Rocky Mountain Spotted Fever. Krill feed baleen whales. Antennae used for touch and taste. Usually gills for gas exchange.