Mayflies, of order Ephemeroptera, is an aquatic group of insects emerging in vast numbers during the months of summer. It belongs to one of the ancient groups of extant insects with origins dating back to greater than 300 million years. They are characterized by extremely short life expectancy.
They are also known by alias names like sandfly, shadfly, fishfly, dayfly, and drake. Most mayflies consume algae, diatoms, organic detritus, and higher plants. However, some species are known to be carnivores.
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There are three types of mayflies −
White Mayfly − White mayflies (Ephoron leukon) are a group of flies that lay eggs in very high numbers resembling a blaze of ice. They mostly appear in the month of August. They are sensitive to light. Their hatching period lasts for two to three weeks.
Giant Mayfly − They belong to the genus Hexagenia and are also known as golden mayflies owing to their yellow and brown appearance. They are mostly found in the eastern part of the United States. They contain two wings that are dark, giant, and triangular along with two filamented tails.
Black Mayfly − They belong to the genus Hexagenia (H. bilineata). In their early stages, the wings appear darker in color which later transforms into shimmery and transparent with age. A dual lateral line is found along their abdomen.
There are four stages in the lifecycle of mayflies.
Egg − A female mayfly produces 50 to 100000 eggs depending upon the species. They vary in size and shape and can be oval, oblong, or round. When laid in water, the eggs may attach themselves to any submerged entity or settle to the bottom. The average hatching time is about two weeks. Sometimes, prolonged periods are also observed under hostile environmental conditions. No growth occurs during this period known as diapause.
Nymph − Nymph, also known as a naiad, is an aquatic immature occurrence and this stage can vary from weeks to a couple of years. During this time, periodic shedding of skin known as molts occur ranging from 1 to 50 times. The occurrence of molts is dependent upon environmental conditions and the species.
Nymphs are characterized by only one claw at the end of each of their six legs. They have two to three slender tails as the body ends. They also contain gills attached to their outer and upper surface of the body, helping them to survive underwater for extended periods.
Subimago − The end of the nymph stage is marked by the splitting of skin into the back and wings, giving rise to Submigo, also known as dun. They take shelter in nearby places, unlike nymph which resides in water. Submigo undergoes overnight skin shedding for a period of one minute to several days, depending upon the species. This final shedding gives rise to the Imago.
They have large eyes and short and bristle-like antennae. The wings of submigo are opaque with a tint of blue, yellow, grey, or olive color. The front pair of wings are triangular while the hind pair is rounded. They have a mottled appearance owing to heavy pigmentation across the veins. The legs and tails of the submigo are also shorter than the imago. Submigo mayflies cannot feed once they enter the winged stage.
Imago − It is the adult stage of the mayflies, also known as a spinner. Although similar in appearance to that of submigo, the image is harder and more vibrant than the former. Their length varies from 2.5 mm to 32 mm including their tails.
The reproductive cycle in mayflies begins with the end of final molting i.e., at the beginning of the imago stage. However, it also marks the death of the mayflies as soon as mating and oviposition occur. In some cases, Hexagenia males may undergo mating twice on successive days. Similarly, few female imagos are capable of retaining the eggs, possibly mating twice on successive days.
Male imagos attract female imagos by performing a mating flight in groups during the sunset. The flight patterns include flying up and forward followed by a downward flight and repeat. As the females join the performance, the males approach them from below, and grasp them through their thorax, completing the mating at the wings.
The male releases the female who deposits the eggs and dies. Some species are ovoviviparous.
Nymphs can survive up to a year or so however, adult mayflies have the record of shortest lifespan on earth of 24 hours only. Barring a few species, they die within 5 minutes of mating. The exceptional groups can survive for a maximum of the second mating cycle on a successive day.
They are an important constituent of our ecosystem and hold economic value too.
Owing to their highest protein content among edible insects, they are consumed by humans worldwide.
They act as a good laboratory organism.
They offer a potential candidate as antitumor molecules.
They are known to clean freshwater through their regulatory mechanism.
They act as a support system for bio-irrigation, bioturbation, cycling, and spiralling of nutrients in freshwater, etc.
They serve as health indicators of the ecosystem.
They ensure nutrient cycling between terrestrial and aquatic systems.
Mayfly belongs to a relatively tiny order of short-lived insects. However, they are important for the ecosystem owing to their services like providing nutrition, remediation, biodegradation, etc. Under the unfavourable effects of climate change, pollution, habitat loss, and invasion, the survival of mayflies faces certain challenges. To maintain a healthy ecosystem, it is important to pay attention to and make efforts to revive the dying population of mayflies.
Q1. What do you understand by the term ovoviviparous?
Ans: Those species of the female mayflies whose eggs hatch within their body as they float over the water surface after mating, and dying.
Q2. What do you understand by the term bioirrigation?
Ans: Bioirrigation refers to the exchange of solutes present in overlying water with those in the sediments by benthic organisms. Benthic organisms are those which live on the ocean floor, either attached to a firm surface or mobile. It plays an important role in sediment biogeochemistry.
Q3. What do you understand by the term bioturbation?
Ans: Bioturbation refers to a disturbance in sediment’s stratigraphy on account of biogenic transport influenced by animals or plants. The causes of bioturbation include ingestion, burrowing, defecation of sediment grains, etc.
Q4. What is the distribution pattern of mayflies?
Ans: There are approximately 3700 species of mayflies known to man, distributed among 20 families. Out of this, nearly 700 are found in North America alone. They are not observed in Antarctica. In high activity areas, the nymphs can be found in densities of 1400 units per square foot.
Q5. What are the major challenges to the life of mayflies?
Ans: Major factors contributing to the extinction of mayflies are increasing pollution, invasive alien species, habitat degradation, and climatic variations.
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