Nectar robbing

[1] Nectar-robbing mammals include the fruit bat[2] and Swinhoe's striped squirrel, which rob nectar from the ginger plant.

[3] Records of nectar robbing in nature date back at least to 1793, when German naturalist Christian Konrad Sprengel observed bumblebees perforating flowers.

[4] This was recorded in his book, The Secret of Nature in the Form and Fertilization of Flowers Discovered, which was written in Berlin.

Secondary robbers often do not have suitable mouth parts to be able to create penetrations into the flowers themselves, nor to reach the nectar without robbing it.

For example, short-tongued bees such as the early bumblebee (Bombus pratorum) are unable to reach the nectar located at the base of long flowers such as comfreys.

Birds are mostly primary robbers and typically use their beaks to penetrate the corolla tissue of flower petals.

Mammal robbers such as the striped squirrel chew holes at the base of the flower and then consume the nectar.

[1] As nectar robbers receive the rewards without direct contact with the reproductive parts of the flower, their behaviour is easily assumed to be cheating.

[1][8][9][10] For example, the proboscis of Eurybia elvina does not come in contact with the reproductive parts of the flower in Calathea ovandensis, but this does not lead to significant reduction in fruit-set of the plant.

[11] In another example, when 80 percent of the flowers in a study site were robbed and the robbers did not pollinate, neither the seed nor fruit set were negatively affected.

[1] The ways that bees distinguish between robbed and unrobbed flowers have not been studied, but they have been thought to be related to the damage on petal tissue after robbery or changes in nectar quality.

[4] Nectar robbing, especially by birds,[16] can damage the reproductive parts of a flower and thus diminish the fitness of a plant.

A good example of an indirect effect is the change in the behaviour of a legitimate pollinator, which either increases or decreases the fitness of a plant.

[20][21] If nectar robbers have an effect (direct or indirect) on a plant or pollinator fitness, they are part of the coevolution process.

[19] Some studies have shown that nectar robbing does not have a significant negative effect on the reproductive success of both male and female plants.

[7] One example is a plant called Catalpa speciosa which produces nectar containing iridoid glycosides that deter nectar-thieving ants but not legitimate bee pollinators.

Another way to use time in defence is to flower only for one day as a tropical shrub Pavonia dasypetala does to avoid the robbing Trigona bees.

A good example of an indirect defence is to attract symbiotic predators (like ants) by nectar or other rewards to scare away the robbers.