Attraction and reward by means of perfumes
This reward-a phenomenon rare in plants-is known for dozens of species of orchids, including some 55 South African species, and bees use it to feed their larvae. The genera Disperis , Pterygodium , Corycium , Ceratandra , Evotella , Satyrium and Pachites , among others, present species reward their pollinators with oils.
Pollination by flies ( miofilia ) is the second most common syndrome among the orchids, with species from 20 families of Diptera recorded as pollinators. The flowers emit scents that resemble the natural food or substrates visiting flies, which are commonly decaying organic material, dung or carrion, in search of food or to lay their eggs. Different floral parts produce putrescent odors or sweet, usually are traps that hold the pollinator, besides having several appendices that attract and bright colors either or resembling meat or some other dye rotten material. The flowers of Stelis hymenantha , for example, emit an intense aroma of fresh menthol. At the base of the lip is produced a substance which strongly adheres to its surface, as a film, similar to the nectar. The flowers of S. immersa , another orchid pollinated by flies, are also fragrant, but with a different flavor, like melon, and unlike the first, the sticky substance is located mainly in the petals and the base of the lip. Visitors to these two species are mainly flies of several families. Most usually remain flies out of the flower'''' examining the viscous liquid on the external surface of the petals. Pollinators in Stelis immersa are female gender a small fly Megaselia ( Phoridae ), which is the only one with the right size for the transfer of pollen. After examining the nectar-like substance, the insect is introduced laterally into the flower and perches on the lip that is in the downward position. When this happens, the lip is raised to press the insect against the pollinarium viscidium and trapping. To exit, fly back and viscidium sticks to your chest. The lip returns to its original position releasing the animal.
The flowers of the species of the subtribes Stanhopeinae and Catasetinae belong to the most fascinating and bizarre of all orchids. They are not the most beautiful, but because of their pollination so particular sometimes have created bizarre flowers pollinated with strange mechanisms. The species of this tribe are pollinated exclusively by male euglossine bees collect fragrances and looking at these flowers. So far no one knows what the males collect and keep these perfumes, because no use for nutrition and protection. It is thought that must be related to the mating rituals of these insects.The way to collect these ingredients are always very similar. The male approaches the source of the aroma, osmóforo , usually sits on the lip and begins to collect with their front paws substances responsible for aroma. In most cases are liquids, in some species in crystalline form. If they are solid, the male first dissolved with secretions from their salivary glands. With long, dense hairs of his front legs, the male collects the liquid present in the lip. If this body is saturated with the aromatic components, the bee leaves the flower to transfer the flavorings with the aid of the middle legs of cavities found in the hind legs. Inside these chambers substances can be stored for long. Different orchid pollinaria stick the (or polynya) to different body parts of these pollinators are attracted chemically to their flowers. 19 Orchids, like other plants, selectively attract a specific group of male euglossine through production of mixtures of species-specific aromas that apparently act asmechanisms of reproductive isolation . Thus, different species of plants attract different groups of pollinators. Even some orchids have flowers morphological changes such that only release the pollinarium when visited by certain species of bees (by size and behavior). For this reason not all euglossine bees visiting an orchid species are effective pollinators of it.
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