Toxins and secondary compounds are likely to act as a defence against nectar robbing because they are often found in floral nectar or petal tissue. There is some evidence that secondary compounds in nectar only affect nectar robbers and not the pollinators. One example is a plant called "Catalpa speciosa" which produces nectar containing iridoid glycosides that deter nectar-thieving ants but not legitimate bee pollinators. Low sugar concentration in nectar may also deter nectar robbers without deterring pollinators because dilute nectar does not yield net energy profits for robbers.