Young Spiders Survive On Meals Of Mother

Some mothers make the ultimate sacrifice for their children. They let them eat her for breakfast, lunch and dinner.

Researcher Theodore Evans and his colleagues from the University of Melbourne report in a recent issue of the journal Nature of a species of spider in which the mother takes maternal care to grisly extremes: The baby spiders survive by consuming their mother while she’s alive.

Evans, who had been studying the behavior of the Australian “social crab spider” or Diaca ergandros, said the mother makes herself available for feeding to prevent sibling cannibalism. Better for her kids to eat her rather then each other to ensure the survival of the gene pool.

The mother spider will lay only one clutch of spiders, usually 40 to 70 eggs at a time, in her lifetime. These spiders are reared and protected by the mother in a nest built by her and her relatives.

“Spiders typically are anti-social animals,” Evans said. “But not the social crab spiders. … They tend to recognize kin. They are willing to share and build nests with them….”

Evans said that, during the first four months, the mother spider will hunt prey to feed her brood, and protect them. But, as time goes by, the kids tend to become more aggressive, but they’re not quite aggressive enough to fend for themselves. So, she sacrifices herself.

By the fourth month, the mother no longer can sustain the children with whatever food she catches, so she hunts one final time, letting them eat all they can, then she devours what’s left. Then she offers herself.

The children start by biting into her arms and legs “where all the blood vessels are” in order to get the essential nutrients, Evans said.

“Also, this way, she can help fight off any potential prey while they’re feeding by biting with her poisonous fangs,” Evans said.

Then, once the arms are no longer able to give, they go for her eyes. The body is always last.

“Preventing sibling cannibalism is very important because this species of spider cannot survive on their own; they live in packs much like wolves,” Evans said. “They have to, because like wolves who hunt moose, the ergandros - which are only 1 centimeter across - like to hunt large beetles and wasps, obviously much bigger than themselves.”

Evans said the baby spiders can feed on the mother for five to six weeks before they head out on their own.