Nature on our doorsteps: The last job of her life …

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into the natural heritage around us and the beautiful biodiversity of the plants and creatures.

Some spiders, like the Crab spider, lay their eggs in late summer and early autumn.

When a female Crab spider is preparing to lay eggs, she first needs to be sure that she has fed really well over the summertime.

She needs to fatten up so much that her abdomen becomes big and round, because once she lays her eggs, she will not eat again before she dies.

When she has grown big enough, she begins to construct a nest for her eggs.

She first chooses a sturdy leaf in a bush and she folds it over.

Using little pieces of silky web like glue, she sticks the edges of the leaf together, forming it into a little triangular pocket.

She then places her sac of eggs inside the pocket and she seals the opening securely with web.

With her eggs safely inside, she takes up a protective position on the folded leaf.

The Crab spider female glues the edges of a leaf together to form a nest for her eggs

She will not leave the nest again, not even to find food for herself.  Her priority is to guard and protect the nest from predators like beetles or earwigs.

As the days pass by and her eggs develop, her big tummy, which first looked stretched and swollen, starts to shrink as she loses weight.

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

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

The mass of spiderlings do not stay around for long.

Too many little wriggling spiders in one place can attract predators like birds, and their mother is so weakened by her long fast that she no longer has the strength to protect them.

The spiderlings drift away individually from the nest site in search of food and a place to hide away for the winter.

Once her spiderlings have all left, the female spider’s job is done.

She too wanders away into the bush, and she dies shortly afterwards.