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
Heliconius charithonia and show superior mimetic diversity to those that do not. Adult butterflies choose their home ranges based on collections of pollen plants. An adult collects pollen by inserting its proboscis into the flower while making particular movements to secure adhesion to the pollen grains. Digestion occurs immediately after ingestion when the pollen makes contact with saliva, and amino acids are dissolved. Optimal amino acid intake occurs through abundant saliva production and gentle and slow mastication. During the night, the butterflies digest pollen since optimal nutritional resources are obtained while resting or sleeping. Pollen feeding is correlated with higher overall fitness.