Kids are so demanding. They need $20 for the movies, they want an electric drum kit for Christmas and when they’re hungry they want you for dinner. And yes, in case you didn’t quite catch that last bit, i’m talking about offspring eating their mother. All of her. While she’s still alive.
Welcome to the real world horror story of a mother Japanese foliage spider.
Our story begins in a humble leaf nest where a Japanese foliage spider lays a single egg sac filled with her 100 expectant baby spiders – she hopes there’s enough room in the nursery and that they’ll all like the gender neutral green she picked out!
For two weeks she carefully tends to her brood until (finally!) they’re ready to hatch and excitedly she helps each one emerge by opening the egg sac and releasing them into the open. At first they’re adorable, squirming around as larvae – but there’s a looming problem. There’s no food in the nest and a lot of hungry mouths to feed…
And suddenly quicker then they arrived, the good times are over. Her 100 little spiderlings suddenly start to moult into mother-eating monsters. With no other food in sight, it looks like Mum’s for dinner and even though she’s alive, the Japanese foliage spider will simply allow her children to eat her. Happy in the knowledge that she’s giving her young the nutrients they need to venture out into the world.
Maternal love and all but seriously, WHAT IS GOING ON HERE? Why on earth would you let your kids eat you?
Turns out eating your mum has a technical term – matriphagy, and it’s perhaps the most extreme form of parental care you can get. The mother Japanese foliage spider gives up herself to feed her young and this provides 3 key benefits:
- The spiders have enough nutrients to grow bigger.
- The spiders also are able to moult into a third and final form with longer legs making them more competitive hunters.
- Lastly, if they eat Mum they don’t have to eat each other. So while there’s still cannibalism at least it’s not sib-cannibalism yay!
So it’s good for the spiderlings, but in actual fact, this matriphagy is not entirely self-less for the mother either. After reproducing, females are very unlikely to be able to do so again because of the energy they’ve expended. Therefore it makes more sense, biologically, to invest everything into this brood so they’ve got the best chance of survival then to run free when you won’t be able to reproduce again.
Still very extreme yes, but if we take away all the anthropomorphism this mother eating madness actually makes sense. Mother foliage spiders only get one shot at motherhood so they really put their back into it. And their legs, and their eyes… They truly make, the most dedicated mothers around.
Toyama, M. (2001). Adaptive advantages of matriphagy in the foliage spider, Chiracanthium japonicum (Araneae: Clubionidae). Journal of Ethology, 19(2), 69-74.