Some plants have come to rely so heavily on ants to spread their seeds about that they offer the insects a tasty treat in exchange for the dispersal service. Seeds of these species bear a lipid-filled structure called an elaiosome, whose sole function appears to be the attraction of ants. A recent study suggests that plant lineages dependent on ants in this way speciate more rapidly than related ant-free lineages.
photo details (both photos): Canon MP-E 65mm 1-5x macro lens on a Canon EOS 50D
ISO 100, 1/160 sec, f13, indirect strobe in a white box