Mayfly

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Ephemeroptera

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Ephemeroptera, an insect of the order Ephemeroptera, is called Ephemeroptera for short^{[4 ]} 。 More than 2300 kinds of mayflies are known all over the world, and more than 300 kinds of mayflies are known in China.^{[3 ]} Small to medium-sized, slender, soft body wall; Mouth chewing type, compound eye developed, 3 monocular; The antennae are short, bristly, and the wings are membranous. When resting, they stand on the back of the body. The front wings are big triangular, and the rear wings are degenerated and smaller than the front wings; The wing veins are primitive, with many longitudinal and transverse veins, which are reticulate. It is named because its adult flies like floating waves.^{[4 ]}

Ephemeroptera is mainly distributed in tropical to temperate regions, and is greatly affected by temperature, water geology, water quality and flow speed.^{[5 ]} The life style of mayfly larvae varies from species to species. Some swim and attach to aquatic plants, some crawl in the sludge at the bottom of the water, some build channels to live in the clay on the river bank, and some have flat bodies and hide under the clear and swift stones. They feed on decaying debris, small algae, protozoa and decaying aquatic plants. Some species are carnivorous and feed on small insect larvae.^{[6 ]} Adults lay their eggs in water, and the eggs are often glued into globular or columnar egg blocks, which fall into the water and then disperse. Each female lays hundreds to thousands of eggs, and some species only lay one egg at a time. The egg development time is usually 1 to 2 weeks, and some need more than a month.^{[7 ]} Ephemeroptera adults don't live long, a few hours or 1-2 days short, and about a week long, so there is a saying of "dying every day".^{[8 ]}

Ephemeroptera has attracted much attention because of its beauty and extremely short life span, and is regarded as a symbol of short and precious life.^{[9 ]} They are a kind of ancient insects and are considered as one of the living fossils. Because of its high sensitivity, mayflies can be used as a yardstick to measure the degree of environmental pollution, which has attracted the attention of biosystemists.^{[10 ]}

Chinese name: Mayfly^{[4 ]}
Latin name: Ephemeroptera
Alias: mayfly 、 Mays^{[4 ]}
circles: Animal kingdom
door: Arthropoda

Outline: Insecta
order: Ephemeroptera
Yamen: Hexapoda
Subclass: Winged subclass
Chinese scientific name: Mayfly

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History of Zoology

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Mayfly

Ephemeroptera is a kind of primitive insect, which originated in the Carboniferous period and has a history of at least 200 million years. It is the most primitive winged insect. It is named mayfly because its adult flies like floating waves. Ephemeroptera has attracted much attention because of its beauty and extremely short life span, and is regarded as a symbol of short and precious life. Its adult life span is not long, short hours or 1~2 days, long about a week, so there is a "life and death" saying.^[2]^{[4 ]}^{[8-9 ]}

morphological character

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Ephemeroptera, an insect of the order Ephemeroptera, is called Ephemeroptera for short 。 It's the most primitive with wings Insects. Small or medium size, slender, body wall Soft. The head is small, the antenna is short, and bristly. The compound eye is developed, and the female compound eye is often far from left to right; The male compound eye is often larger and close to the left and right, and the upper and lower eyelids of each compound eye are often different. Generally, the upper eyelids are larger than the lower eyelids, and there are also two parts completely separated. 3 for each eye. The mouthpiece is chewing type, because adults do not feed and have no chewing ability, Maxilla Degeneration disappears, and the jaw also degenerates, often with chin whiskers. The thorax is the largest in the midthorax, and both sub adults and adults can fly in the air. The adult body wall is thin and shiny, usually white and yellowish. With one or two pairs of wings, the vibration frequency is very small when flying. The front and rear chest are small but not significant. There are two pairs of wings, which are triangular, fragile, membranous. Most of them have large front wings and small rear wings. Some have degenerated rear wings and stand on the back of the body when resting. Mayfly vein The joints of Xiangji and its wings are underdeveloped, and the veins are the most primitive. There are many longitudinal and transverse veins, which are reticulate. The surface of the wings is folded and fan-shaped. Feet are thin and weak, only for climbing. Tarsal segment is 1-5 segments, with one pair of claws at the end. There are only 11 segments of abdomen, and only narrow annular backplane exists in the 11th segment. There is a pair of clasps formed by the lengthening of the forefoot on the trailing edge of the male 10th segment, 3-4 segments, and a few 1 segment, which are used to catch the female insect in flight. There are two pairs of short simple male stems on the inner side. There is one pair of female genital pores, which open on the ventral surface of the 7th and 8th abdominal segments. The ovaries are arranged in segments. Bisexual reproduction Hole average In pairs. At the end of the abdomen, there is a pair of segmented filament like tail whiskers, and the 11th segment backplate is often extended to form the middle tail filament. The tail whiskers and middle tail filaments are slender and multi segmented, similar to those of the order Thysanura^[1] 。^{[4 ]}

Mayfly Naiad There are two more specialized systems:

Long tailed mayfly (6 sheets)

Flat And fish type. The former uses heptageniidae (Heptageniidae) as a representative, the insect body is flat, that is, the width of the insect body is far greater than the thickness of the back and abdomen of the body. For convenience, the habitat of mayfly larvae can be divided into two types, one is still water area, the other is flowing water area. Still water areas are represented by lakes and ponds. The areas above the light compensation depth in the still water area can be further divided into three categories, namely, in the still water body, on the surface of the sediment, and in the sediment^[1] 。

Life habits

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Mayfly larva

Mayfly larva（ Naiad ）Aquatic, living in Freshwater lake Or in a stream. In spring and summer, from afternoon to evening, there are often groups of male insects to "fly in marriage", and females fly into the group alone to pair with males. They lay eggs in water. The egg is small, oval, with various colors, and its surface is textured and sticky, which can be attached to the debris at the bottom of the water. The larval stage lasts for several months to one year or more, and molts 20-24 times, most of which can reach 40 times. One or two pairs of blackened wing buds can be seen in mature larvae. Paired on both sides or back Tracheobranch It is a respiratory organ suitable for living in water. They eat higher aquatic plants and algae, and some species feed on bottom debris in autumn and winter. They often climb and crawl in still water, burrow in bottom mud, or absorb Gravel Take shelter. After fully growing, the juveniles either rise to the water surface, or climb to the rocks or plant stems at the water edge, and emerge after sunset Subadult 。 Similar to adults, sub adults have developed wings, but the body color is dim, the wings are opaque, the trailing edge has obvious marginal hairs, and the male clasper is not curved. After leaving the water, stay on the plants near the water area. Normal longitude 24 hour The left and right molts into adults. This phenomenon of molting after the appearance of adult body in the individual development is the only one in Ephemeroptera among winged insects. This type of metamorphosis is called protometamorphosis. Most mayfly larvae focus on feeding: some filter feed animals, collecting suspended food with bristles on their forelegs and mouthparts; Some eat plants or other biological debris, which scrape algae from rocks or other surfaces like bulldozers; A few specialize in predation. Adults do not eat and have a short life span. They usually live for a few hours to several days“ the brevity of life ”The statement of. Ephemeroptera adults are responsible for mating and reproduction in their short lives.^[1]^{[6 ]}

Distribution range

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Ephemeroptera is mainly distributed in tropical to temperate regions, and is greatly affected by temperature, water geology, water quality and flow speed.^{[5 ]}

Growth and reproduction

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Ephemeroptera adults lay their eggs in water, and the eggs often stick into globular or columnar egg blocks, which fall into the water and then disperse. Each female lays hundreds to thousands of eggs, and some species only lay one egg at a time. The egg development time is usually 1 to 2 weeks, and some need more than a month.^{[7 ]}

Ephemeroptera sub adults

The mayfly metamorphosis type is Protometamorphosis The whole life goes through four stages: egg, larva, sub adult and adult Winged subclass The more primitive metamorphosis type is only found in Ephemeroptera. In particular, the transformation from larva to adult requires a "sub adult stage", when the sub adult is completely similar to the adult. The sub adult stage lasts for a short time, and generally becomes an adult after several minutes to one day. Female insects lay eggs in water in temperate regions, and different kinds of mayflies eclosion in summer. Ephemeroptera in tropical areas is seasonal in eclosion, or eclosion in reference to the lunar phase of the year. In order to complete the penultimate molting (eclosion), some of the last instar larvae leave the water body, and some small species eclosion directly on the water surface. They first molt into sub adults with thin wings. Most sub adults molt again after a short flight, becoming adults with transparent wings, mature sexual development, and often used as "spin bait" by fishermen. For some species, the interval between the two molts is several minutes, while for others, it can be as long as several hours. The adults of mayflies do not eat. After molting, their digestive tracts are full of air - before the last molting, both ends of the midgut heal to form a closed sausage shaped balloon, which is full of air, so that the larvae can easily rise to the water surface. The egg is small, white, green or light brown, round or oval. One end of the egg often has a cap attached to it, or sticky filaments protrude from the surface of the egg. Juveniles are aquatic and often flat. The structure of the upper jaw is primitive, with only one articular process, a prominent chewing surface on the inner edge of the center, and a pair of intermaxillary jaws on both sides of the tongue. Compound eye and monocular developed; The antenna is long and filiform. There are paired tracheobranches in the 1st to 7th segments of the abdomen, and 2-3 tail filaments. The tracheobranch is a respiratory organ suitable for living in water. The juvenile stage is generally 1-3 years, and most of them have one or two or three generations every year. They can complete development in 10-15 days in warm areas. Generally, 20 to 24 times of peeling, and more than 40 times. Juvenile feeding higher plant And algae, and a few species prey on aquatic arthropods. Mature juveniles generally rise to the water surface, or climb to the rocks or plant stems near the water, and emerge into "sub adults" after sunset. At this stage, they are similar to adults, but their wings are opaque or translucent. Their body surface, wings, and feet are often covered with fine hairs and fringed tassels. Their body color is darker than that of adults, and their forelegs and tail whiskers are short. They are inactive and in a resting state. They cannot mate. The length of sub adult stage is related to the length of adult stage. The shorter the sub adult stage is, the shorter the adult life span is; The sub adult stage is longer, and the adult stage is longer. Ephemeroptera will peel after becoming an adult. Adults do not feed,^[1] 。

Subspecies distribution

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More than 2300 kinds of mayflies are known all over the world, and more than 300 kinds are known in China 。^{[3 ]}

Key values

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Ephemeroptera is an ancient insect, which is considered as one of the living fossils.^{[10 ]}

Ephemeroptera is very sensitive to anoxic and acidic environment, so the number of Ephemeroptera in an area can be used as a yardstick to measure the environmental pollution in this area. Acid rain in many parts of North America and Europe once killed the larvae of ephemera habitat, which also reduced the number of local fish flocks - because ephemera larvae are the main food of fish flocks. In 1675, the Dutch biologist Jane Wonmaidan gave a detailed description of a kind of mayfly. At that time, the number of this kind of mayfly was very rich in the Netherlands. But now, no trace of this kind of mayfly can be found in the whole of Western Europe, because the larvae of mayflies are extremely sensitive to environmental pollution. Therefore, the existence of mayflies can be used as an important standard to identify water quality, It has attracted the attention of biosystemists.^[1]^{[10 ]}

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