Nature on our Doorsteps: A mother spider’s sacrifice

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into nature on our doorsteps and the beautiful biodiversity of its plants and wildlife.

GARDEN Crab spiders do not build webs.

Instead they ‘wait-and-grab’.

They will sit still and wait, pouncing suddenly on unlucky prey such as flies or bees.

The spider will quickly inject them with strong venom and will suck away their life juices.

Before she lays her eggs, the female Crab spider must first grow as big as she can.

It can take up to three weeks before her eggs hatch, and she normally will not feed again once her eggs are laid.

The mother spider uses silky web to glue a folded leaf together to form a nest for her eggs.

She therefore needs a huge reserve of energy to keep her strong while she protects her developing eggs.

When she is big and fat enough, the female begins to construct a nest for her eggs.

She folds over a leaf, forming it into a little pocket, and places her egg sac inside.

Using sticky lines of spider’s silk, she glues the leaf edges together, sealing it tightly.

She takes up a protective position on the folded leaf and will not leave, even to find food.

Her priority is to protect the nest from predators like beetles or earwigs.

As the days pass, her big tummy, which first looked fat and swollen, starts to shrink.

By the time the eggs hatch three weeks later, this tummy now looks deflated and wrinkled.

When she senses movement inside the nest, she makes a small opening in the glued leaf and her tiny spiderlings emerge out into the air.

Although they may be a darker colour initially, they are little replicas of their mother.

The spiderlings do not stay around for long.

Too many little moving spiders in one place can attract predators like birds or wasps, and their mother is so weakened by her long fast that she can no longer protect them.

Once her spiderlings have all left to fend for themselves, her job is done and the mother spider endures the ultimate sacrifice.

She dies shortly afterwards.

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