Posted: Thursday 11th December 2014 by The Isles of Scilly Wildlife Trust

Cellar Spider with Egg SacCellar Spider with Egg Sac

Volunteer Ranger Rhianna Pearce talks to us about a commonly seen visitor to our homes, the cellar spider.


During the winter months you are likely to find an abundance of spiders creeping into your homes to escape the harsh weathers outside. Here on Scilly it is more than likely that the spiders lurking in the corners of your room are cellar spiders, or more commonly called ‘daddy long-legs spiders’. These spiders are commonly mistaken for harvestmen, another creature with 8 long spindly legs. Harvestmen  however,  are not spiders as they only possess 2 eyes and lack the power to produce silk. It is far more likely that the creature with a small rounded body and long legs hanging from a web in your home will be a cellar spider.

There is a common confusion surrounding these spiders, with a similar confusion surrounding crane flies, that they have been thought to have the most venomous bite amongst spiders. In actual fact though, they cannot penetrate human skin because their fangs are too small, furthermore these spiders do not possess poison glands. They are relatively harmless to humans as they are not known to bite.

If you disturb a cellar spider in its web it will not try to attack you or run away. Instead, you will see it hanging upside down from its legs, frantically spinning in circles for about half a minute. This behaviour is known as whirling. It may seem like a rather peculiar reaction, but no behaviour is without reason. It is thought that cellar spiders are predated on by visual predators such as the jumping spider, where it pinpoints the body in order to attack. Whirling confuses the attacker and makes it difficult for them to focus on the spider.

There are two adult cellar spiders currently living above my bed. One of which has only 5 legs. Cellar spiders typically eat other insects, such as moths and flies, but they can interestingly resort to cannibalism when food sources are scarce. They do this by making their way into another spider’s web pretending to be prey. When the other spider comes to investigate, it will then strike by cocooning it in silk. Cellar spiders have long legs adapted to wrap up its prey whilst keeping its body at a safe distance allowing it to attack more venomous spiders relatively safely.

You may think cellar spiders are seemingly boring creatures at first sight but their remarkable behaviours make this harmless creature truly fascinating to watch.

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