Pollination rigida", this allows the plant to self-pollinate, which is useful when biotic pollinators in the environment have decreased. It is possible for a plant have varying pollination methods, including both biotic and abiotic pollination. The orchid "Oeceoclades maculata" uses both rain and butterflies, depending on its environmental conditions. More commonly, pollination involves pollinators (also called pollen vectors): organisms that carry or move the pollen grains from the anther of one flower to the receptive part of the carpel or pistil (stigma) of another. Between 100,000 and 200,000 species of animal act as pollinators of the world's 250,000 species of flowering
Pollen periods of pollen rains, allows fungi to decompose nutritionally scarce litter. Some species of "Heliconius" butterflies consume pollen as adults, which appears to be a valuable nutrient source, and these species are more distasteful to predators than the non-pollen consuming species. Although bats, butterflies and hummingbirds are not pollen eaters "per se", their consumption of nectar in flowers is an important aspect of the pollination process. Bee pollen for human consumption is marketed as a food ingredient and as a dietary supplement. The largest constituent is carbohydrates, with protein content ranging from 7 to 35 percent depending on the plant