Why do spiders eat their own webs?
Spider webs come in a range of forms, with some spider webs being used for many years and others being rebuilt each day. The latter often eat their old webs as they dismantle them, but why?
Only 17 of Britain’s 37 families of spiders use webs to capture their prey. These webs come in many different forms – from the much-admired orb webs of garden spiders and their relatives, to the much less welcome tangle webs of daddy-long-legs spiders.
Some types of webs are enduring structures – the often extensive funnel webs of large house spiders, for example, can last for years and accommodate a succession of different occupants.
By contrast orb webs, produced by just four families of British spiders, are more fragile. Wind and rain damage their structure, while the gluey coating on the spiral thread that ensnares flying insects is rendered ineffective by pollen and dust. As a result the webs are often rebuilt every night – an operation requiring the manufacture of some 20 metres of silk.
To recycle the amino acids that make up the silk proteins, some orb-web-spinners ingest the silk as they systematically dismantle their damaged webs. Other species simply discard the old silk but one American species uses it to wrap its egg sac.
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Main image: Garden cross spider on its web, UK. © Olivier Roland/EyeEm/Getty