Pollination traps or trap-flowers are plant flower structures that aid the trapping of insects, mainly flies, so as to enhance their effectiveness in

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds ...

. The structures of pollination traps can include deep tubular corollas with downward pointing hairs, slippery surfaces, adhesive liquid, attractants (often deceiving the insects by the use of sexual attractants rather than nectar reward and therefore termed as deceptive pollination), flower closing and other mechanisms. In many species of orchids, the flowers produce chemicals that deceive male insects by producing attractants that mimic their females. The males are then led into structures that ensure the transfer of pollen to the surfaces of the insects. Orchids in the genus ''Pterostylis'' have been found to attract male fungus gnats with chemical attractants and then trap them using a mobile petal lip. The general observation of insects being trapped and aiding pollination were made as early as 1872 by

Thomas Frederic Cheeseman Thomas Frederick Cheeseman (8 June 184515 October 1923) was a New Zealand botanist. He was also a naturalist who had wide-ranging interests, such that he even described a few species of sea slugs (marine gastropod molluscs). Biography Chee ...

and did not go unnoticed by

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...

who examined the adaptations of orchids for pollination. Slipper orchids have smooth landing surfaces that allow insects to slide into a container from which a window of light leads the insect outwards through a narrow passage where the pollen transfer occurs. The structures found in large flowers such as those of ''

Rafflesia ''Rafflesia'' () is a genus of parasitic flowering plants in the family Rafflesiaceae. The species have enormous flowers, the buds rising from the ground or directly from the lower stems of their host plants; one species has the largest flowers i ...

'' and some ''

Aristolochia ''Aristolochia'' () is a large plant genus with over 500 species that is the type genus of the family Aristolochiaceae. Its members are commonly known as birthwort, pipevine or Dutchman's pipe and are widespread and occur in the most diverse clima ...

'' are also evolved to attract and trap pollinators. Trap-flowers that produce deceptive sexual chemicals to attract insects may often lack nectar rewards. Many fly-trapping flowers produce the smell of carrion. Pollination traps interaction with pollinators Pollination traps plants relies on pollinators such as flies, wasps, bees and more for their reproductive process. The interaction between both of the organism can be mutualistic relationship or commensalism relationship. Plants have evolved unique structures in order to attract and trap the insects that will be responsible to disperse their genetics to another plant. Psychoda fly’s life cycle There is a large number of different flies that the arum plant attracts to its trap. One of the main flies that successfully pollinate for the plant is Psychoda flies also known as the drain flies. These small flies have a short holometabolous life cycle that’s completed within 21 to 27 days: egg, larval, pupal, and adult life. The eggs are deposited on wet or moist soils typically on the sides of drains or other surfaces and hatch in less than two days. Larvae are slender, white to creamy brown. Depending on the temperature this stage can vary from 9 to 15 days. Once they develop certain characteristics, they are ready to pupae. A yellow to brown pupa with small horns is formed and requires 24 to 48 hours before emerging. In the beginning of spring and peaking in late summer, drain flies are on the look out for food. They feed on decaying organic material which is what the arum plant utilizes. Psychoda interaction with Arum plants Flowers often have a sweet fragrance, but the flowers of the Arum plant, excude a rancid smell of ammonia and excrement. Based on its scent, the plant is able to attract drain flies, but what makes them irresistible is their purple rod. A combination of warmth and rancid smell that is emitted in the center of plant creates a perfect bait for the flies. As the flies are lured, they will tumble down the slippery walls into the lower chamber where they are trapped bristles above them. As the male flower opens up to release the flies it covers the flies with pollen and secretes sugary nectar in return. Now the fly will visit another plant of the same species and fertilize. This causes a mutualistic relationship as both will benefit from this trap. Euglossine bee’s life cycle There are around 200 different known orchid bee species. As many other pollinators, these bees collect nectar, pollen and resin from plants however, the Euglossine bees’ males also collect scents to create a right mixture of smells to attract females. They are also known as orchid bees and have four stages to complete, eggs are curved in shape that will hatch approximately 3 days. Larvae take up to 25 days to mature and pupate. The pupa stage lasts about 35 days after which adults emerge, living for 6 weeks to 3 months. Adult Euglossine bees look for mates, and their perfume-seeking behavior gives the Cypripedium orchid plant a resource to set up its trap. Euglossine bee interaction with Orchid Orchids that attract Euglossine bees secrete scented oils, but while accessing these, the bees slip and into a water-filled bucket. To escape the bucket, the bee must crawl up a narrow tunnel, during which the plant attaches pollen sacs onto its back. The escaped bee will visit another orchid and drop the pollen, fertilising it. This is another mutualistic relationship as orchid bees will be covered in oils to find a mate and the pollen sacs will be delivered to another plant. Many members of the genus ''

Arum ''Arum'' is a genus of flowering plants in the family Araceae, native to Europe, northern Africa, and western and central Asia, with the highest species diversity in the Mediterranean region. Frequently called arum lilies, they are not closely ...

'' trap pollinators and the specific mechanisms vary with the insects involved.

Species of the genus ''

Cypripedium ''Cypripedium'' is a genus of 58 species and nothospecies of hardy orchids; it is one of five genera that together compose the subfamily of lady's slipper orchids ( Cypripedioideae). They are widespread across much of the Northern Hemisphere, i ...

'' (lady slippers) of orchids trap insects temporarily to ensure pollination. Plants in the genus ''

Ceropegia ''Ceropegia'' is a genus of plants within the family Apocynaceae, native to Africa, southern Asia, and Australia. It was named by Carl Linnaeus, who first described this genus in his ''Genera plantarum'', which appeared in 1737. Linnaeus referre ...

'' attract pollinating small flies (usually female) in a wide range of families, including

Milichiidae Milichiidae are a family of flies. Most species are very small and dark. Details of their biology have not yet been properly studied, but they are best known as kleptoparasites of predatory invertebrates, and accordingly are commonly known as fr ...

Chloropidae The Chloropidae are a family of flies commonly known as frit flies or grass flies. About 2000 described species are in over 160 genera distributed worldwide. These are usually very small flies, yellow or black and appearing shiny due to the virtu ...

Drosophilidae The Drosophilidae are a diverse, cosmopolitan family of flies, which includes species called fruit flies, although they are more accurately referred to as vinegar or pomace flies. Another distantly related family of flies, Tephritidae, are true f ...

Calliphoridae The Calliphoridae (commonly known as blow flies, blow-flies, carrion flies, bluebottles, greenbottles, or cluster flies) are a family of insects in the order Diptera, with almost 1,900 known species. The maggot larvae, often used as fishing ba ...

Ephydridae Ephydridae (shore fly, sometimes brine fly) is a family of insects in the order Diptera. Shore flies are tiny flies that can be found near seashores or at smaller inland waters, such as ponds. About 2,000 species have been described worldwide, in ...

Sciaridae The Sciaridae are a family of flies, commonly known as dark-winged fungus gnats. Commonly found in moist environments, they are known to be a pest of mushroom farms and are commonly found in household plant pots. This is one of the least studie ...

Tachinidae The Tachinidae are a large and variable family of true fly, flies within the insect order Fly, Diptera, with more than 8,200 known species and many more to be discovered. Over 1,300 species have been described in North America alone. Insects in t ...

Scatopsidae __NOTOC__ The minute black scavenger flies or "dung midges", are a family, Scatopsidae, of nematoceran flies. Despite being distributed throughout the world, they form a small family with only around 250 described species in 27 genera, although m ...

Phoridae The Phoridae are a family of small, hump-backed flies resembling fruit flies. Phorid flies can often be identified by their escape habit of running rapidly across a surface rather than taking to the wing. This behaviour is a source of one of thei ...

, and

Ceratopogonidae Ceratopogonidae is a family of flies commonly known as no-see-ums, or biting midges, generally in length. The family includes more than 5,000 species, distributed worldwide, apart from the Antarctic and the Arctic. Ceratopogonidae are holomet ...

, and the pollinaria always attach to their probosces. An analysis of the scents emitted by ''Ceropegia dolichophylla'' showed the presence of spiroacetals which are rare in plants and common among insects. Milichid flies, which are kleptoparasites of arthropod predators, are attracted by these chemicals and become the pollinators of these plants.

References

{{reflist Kazilek. “Bee Jeweled.” Kazilek, 4 Dec. 2012, askabiologist.asu.edu/explore/orchid-bees. “Euglossini.” Wikipedia, Wikimedia Foundation, 3 Nov. 2020, en.wikipedia.org/wiki/Euglossini. Arum: Pollen. (n.d.). Retrieved December 16, 2020, from https://www.britannica.com/video/180425/fly-plant-Arum-pollen NatGeoWild. (2015, September 8). An Orchid's Trap , Wings of Life. Retrieved December 16, 2020, from https://www.youtube.com/watch?v=_uHJGdTgtXE Pollination