Motherhood typically entails sacrifice, but for most species, the altruism is temporary. Eggs are laid, the young leave the nest, life goes on. Not so for Stegodyphus lineatus, a velvet spider that inhabits Israel's Negev Desert. S. lineatus practices the most extreme—and permanent—form of maternal devotion: matriphagy, in which offspring consume their mother.

Entomologists have wondered about the gory details of this caregiving strategy for years. Is the mother simply eaten as is, or does she prep her innards to make them go down easy? The latter turns out to be the case. Her tissues begin degrading before her young have even hatched, according to research published in the Journal of Arachnology. “Everything is really reprogrammed, as if she's planning ahead,” says Mor Salomon, an entomologist then at the Hebrew University of Jerusalem.

Salomon and her colleagues examined microscopic cross sections of female velvet spiders at each stage of the reproductive process. The tissues began showing light signs of degradation immediately after the egg sac was laid. Then, when the babies emerged 30 days later, the degeneration intensified. “Where the boundary of an organ was very clear, in the next picture you see it becomes blurry, and in the next one, it's gone,” Salomon says. That breakdown allows the spider to regurgitate portions of her liquefied gut to feed her growing young.

As early as nine days after hatching, the mother stops regurgitating, and the juveniles descend on their still living mother for a final family meal. They suck dry all remaining fluids and then vacate the nest, leaving behind the husk of her exoskeleton. Within a year the matured females will pay that maternal largesse forward—offering up their own bodies to the next generation.