Zoology

Mayfly Life Cycle



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I’ve always been a naturalist at heart, and my Amazon orders are full of books about bugs, birds and other creatures. My most recent order contained a book called “How Long Things Live & How They Live as Long as They Do” by Anthony D. Fredericks. The book is arranged from the shortest-lived creature (the mayfly) to the longest (the hydra.) According to Mr. Fredericks’ book, the mayfly lives just 5 minutes.

There are more than 2,000 species of mayfly. Mr. Fredericks was referring to the female American sand burrowing mayfly, Dolania Americana. Although it’s true that this species spends a very short time as a mature adult, they spend a year or more as larvae or nymphs passing through as many as 50 molts, preparing for their brief adulthood when they mate, lay eggs and then die.

Dream as if you'll live forever. Live as if you'll die today. ~James Dean

Mating

Mayfly larvae live in water where they feed and molt. At the last molt, their intestinal tract is sealed at both ends, creating an internal balloon of air that makes them rise to the top of the water. The males form swarms in calm weather, performing an aerial dance where they alternately rise and then glide downward. This isn’t a courtship dance - there is not time for that - they are simply searching for females. Male mayflies have specialized compound eyes pointed upward to help them locate a mate. When he spots a female he quickly grabs her from below and the brief copulation takes place as they drift toward the ground.
 
We cannot waste time. We can only waste ourselves. ~George M. Adams

Laying Eggs

Once mating is complete, the female immediately lays her eggs in water. Some species release the eggs as a mass, while others repeatedly touch the tip of their abdomen to the surface of the water, releasing packets of eggs. A few species dive below the water to lay their eggs. Mayflies prefer moving water, so the eggs often have sticky filaments or adhesive discs that stop the movement downstream.

Parthenogenesis

There are as many as 50 species of mayfly that reproduce parthenogenetically. In this type of reproduction, the female produces fertilized eggs without mating. In a few species that reproduce this way there are no males of the species, only females. In the final molt, the insects already contain fully formed larvae, ready to hatch and begin the cycle again. 

Mayfly Larvae

Superficially, a mayfly larva resembles a silverfish. His function is to eat and molt, and he spends up to three years, passing through as many as 50 molts, although the average is 15 to 25. Some are filter feeders, depending on water movement to provide a steady stream of suspended matter. Others scrape algae from rocks and other surfaces. A few are carnivorous predators.

Mayfly larvae breathe through as many as nine pairs of gills along the sides of their abdomen. Some species have movable gills that they use as paddles to help them move through water. Species with immovable gills live in moving water with a strong current.

Between the last larval stage and the mature adult stage, mayflies enter a pre-adult stage that is unique to mayflies. These pre-adults are called subimagos, and the purpose of this life stage is unknown. In some species the stage lasts just a few minutes while in others it lasts a day or two. 
 
Paleopteras

Mayflies and dragonflies are classed together as Palaeopteras because they don’t have a wing-flexing mechanism. All other flying insects are classed as Neopteras. Paleopteras are the most ancient surviving flying insects. They first appeared between 354 and 295 million years ago. Originally, the larvae were terrestrial, becaming aquatic about 248 million years ago.

Mayflies and dragonflies spend most of their adult lives in the air. On close inspection you can see several other similarities. Both insects have wings that contain a rich network of veins, giving them a lacy appearance.

Pollution Indicators

Many mayfly species are very sensitive to pollution factors such as acidity and low oxygen levels in the water. The species that inhabit a body of water provide a valuable measurement of pollution, and are used in the evaluation of overall water quality. Acid rain has reduced mayfly populations in some areas. Because many fish feed on mayfly larvae, reduced mayfly populations result in reduced fish populations.

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