A spider's web covered in water droplets. This type of web, known as an orb web, is aimed exclusively at catching flying insects. An average orb web may contain 20 metres of silk fixed at 1,000 junctions, yet still weighs less than half a milligram. The web needs constant renewal as its threads become damaged by prey, and the adhesive properties of the viscid, sticky spirals are reduced after a couple of days.