Mothercare spiders

The Mothercare spider (Theridion sisyphium), common in the UK and continental Europe, has earned its name by the way the females look after their young.

Very small and strikingly marked, Mothercare spiders often pitch their webs in thistles and gorse, whose spines offer a defence against predators, as well as being useful for anchoring the web. The contrasting brown/black and white patterns on the abdomen turn out to be an effective camouflage, as they break up the shape of the spider.

Within the web, the female spider builds a dense silk retreat among leaves and leftovers of eaten insects. Here the spiderlings will hatch from a blue-green egg-sac. In their first days they are fed by their mother, who regurgitates digested food into their mouths, behaviour we associate with birds. While nestlings signal their hunger by opening their bills wide, baby Mothercare spiders clutch at their mother’s legs to remind her it’s time to eat again. Soon they will be tucking into whole insects, which the mother has softened for them by breaking down the tough exterior. The spiderlings then begin to help catch the prey with their own silk.

The advantage of this intensive nurturing is that Mothercare spiderlings grow extremely quickly. In contrast, the mother loses weight and shrinks.

The photograph shows a female Mothercare spider with an egg-sac in her retreat, where you can see remnants of past meals.  It was taken by James Lindsey and there are many more fascinating images on his Ecology of Commanster site.

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