I’ve heard of mothers that eat their own children, as well as ones that let their children eat them, but I’ve never come across an aunt that is also willing to be consumed by her sibling’s kids. The African velvet spider is one of the few social spider species, living in large communal nests that consist of hundreds of spiders. Their main task is taking care of the baby spiders, so that their lineage can continue to live on. Mother spiders will look after their babies with the assistance of other, closely related virgin female spiders, kind of like the aunts of their kids. The difference between these aunts and the kind of aunt us humans are familiar with is that, like the mother, they are willing to let the children eat them if food is scarce, along with doing all the other child-rearing tasks. The world of insects is rife with insects that eat other insects that are supposed to have a close relationship with them, such as mates and parents. This is something that us humans find pretty alarming, but this is taking sacrifice to a whole new level.
Velvet spiders are almost ant-like in their social behavior, working together for the good of the nest doing tasks like hunting together, defending the nest, as well as sharing parenting responsibilities. But these spiders go way further than any other insect or arachnid species I’ve heard of when it comes to what they are willing to do for their children. All the females share in the parenting duties. This includes the unmated females helping to tend the children of the other mother spiders. It’s kind of like how an aunt might help take care of her nieces and nephews, except in a much more intense manner. These spiders only live for one year, and in that one year only forty percent of the females reproduce, so it makes sense that the others are expected to pitch in. This includes tending egg sacs, feeding the kids through regurgitation, and even matriphagy, a fancy term for letting your sister’s kids eat you. Usually this kind of self-sacrifice is reserved for the actual mothers, but in the velvet spider home everyone has to pitch in even if it means lying there while a group of baby spiders that aren’t even your own eat you alive.
So, why the heck do they do this you ask? Well, it has to do with the survival of the species. Like in ant and bee colonies, there is a high degree of genetic relatedness among the members of velvet spider nests. Basically, this means that pretty much everyone is related in some way because they only have other members of the nest available for mating. Since they all share the same genes and the level of reproduction is so low, it benefits everyone to perform these sacrificial acts so that the family lives on. Thankfully, us humans did away with all that inbreeding stuff a long time ago…mostly…
Do you know of other insects that have similar practices, such as mothers eating children or children eating mothers? What purpose do you think that behavior serves in their case?