Tannin-resistant chafer larvae change germinating acorns into long-term food stores

Vertebrates excise embryos from rapidly germinating seeds to create long-term food stores—a sophisticated cognitive behavior long considered a vertebrate specialization. Here we challenge this paradigm by demonstrating that larvae of the flower chafer Potosia brevitarsis employ an ecologically convergent strategy to exploit acorns of Quercus variabilis, which germinate rapidly and contain high tannin concentrations. Field surveys showed that 19.3% of naturally buried acorns had precisely excised embryos, with cavities sufficiently deep to destroy the embryonic axis and prevent germination. Behavioral experiments confirmed that larvae first consume the protruding radicle, then excavate the embryo while leaving the seed coat intact, creating non-germinating ‘zombie acorns.’ Acorn supplementation dramatically enhanced larval growth and reduced mortality, confirming fitness benefits. Crucially, we isolated tannin-degrading bacterial strains from the larval gut, with spatially structured communities across foregut, midgut, and hindgut. This tripartite interaction—larval behavior preventing germination coupled with gut microbiota detoxifying tannins—allows P. brevitarsis to overcome dual plant defenses, representing remarkable convergent evolution across animal phyla mediated by microbial symbiosis.