Mayflies
Mayflies
Ecological and economic importance of mayflies
Mayflies or shadflies are aquatic insects in the order Ephemeroptera. There are several thousand species of mayflies, distributed among 20 families. Mayflies have a relatively protracted nymphal stage, which occurs in freshwater habitats. The adults are a short-lived stage during which dense aggregations of animals engage in a frenzied procreation, needed to perennate the species in its local habitats.
Biology of mayflies
Mayflies have a simple metamorphosis, with three life-history stages: egg, nymph (or naiad), and adult. The nymphal stages are numerous and relatively protracted, generally lasting for at least one year. Mayfly nymphs occur in aquatic habitats, and account for
most of the lifespan of mayflies. Some species have as many as 28 nymphal molts. The last, pre-adult stage occurs when a nymph rises to the water surface, molts, and develops into a winged form called a subimago, which flies a short distance, and usually rests on vegetation. Within a day or so, the subimago molts into the terrestrial, sexually mature adult stage, which is generally found in close proximity to the aquatic nymphal habitat. Mayflies are the only insects that have an additional molt after they have developed functional wings.
Mayflies have soft, elongate bodies, with two or (most commonly) three, distinctive, threadlike appendages projecting from the end of their abdomen. Adult mayflies have short antennae and many-veined, roughly triangular membranous wings. The wings are held erect and together over the body when the mayfly is at rest, and cannot be folded up as in most other orders of insects. The aquatic mayfly nymphs have distinctive, leaf-shaped appendages on the sides of their abdomen that serve as gills for the exchange of respiratory gases.
Larval mayflies are aquatic in freshwater, and have mouthparts adapted for feeding on algae and other relatively soft organic materials. Most mayflies are herbivores or detritivores, but a few species are carnivores of other aquatic invertebrates. Because they do not feed, adult mayflies have only vestigial mouthparts. Mayflies have large, compound eyes, and in many species the males are larger than the females, and have forelegs adapted for grasping the female during the nuptial (mating) flight. In most species the forewings are relatively large, while the hindwings may be absent, or are reduced in size compared with the forewings.
Adult mayflies do not feed and live only for a few hours or days. This fact is reflected in the Latin root of the scientific name of this group of insects, Ephemeroptera, which refers to the highly ephemeral nature of the adult stage. The sole purpose of adult mayflies is procreation. To achieve this goal, adults of particular species emerge synchronously within a brief period of time. Adult mayflies sometimes occur in spectacularly large aggregations, in which the animals mate and deposit their eggs to water in frenzied swarms, and then die soon afterwards. Most mayflies in the swarm are males. The females fly briefly into the swarm, find a mate, and they couple then leave to copulate and lay their eggs.
Ecological and economic importance of mayflies
Sometimes, the mass emergences of adult mayflies can involve extremely large numbers of animals. During the brief times when mayflies are very abundant, some people may view them as a nuisance, because the insects seem to be flying everywhere and can be bothersome because of this, or because their bodies accumulate abundantly on beaches, streets, window screens, and in other places. Rarely, the accumulated biomass of mayfly bodies can represent a traffic hazard, by making roads rather slippery. However, this is quite a rare event, and in general mayflies should not be thought of as a nuisance. Mayflies are rarely abundant enough to be a bother. Almost always, they are a harmless part of the natural world.
Mayfly nymphs are an important component of many freshwater ecosystems. Their grazing is important in preventing the buildup of a large biomass of aquatic algae and detritus, and in nutrient cycling. Because mayflies can be quite abundant in many habitats, they are an important food for many species of predators.
Mayfly species are rather particular in their choice of habitat, and in their tolerance of environmental conditions, such as the water temperature and chemistry. Because of their specific habitat requirements, mayfly
KEY TERMS
Indicator —In environmental science, a surrogate measurement related to an important aspect of environmental quality. Mayfly species, for example, are often studied as indicators of water pollution.
Simple metamorphosis —A developmental series in insects having three life-history stages: egg, nymph, and adult.
species are often studied by aquatic ecologists as indicators of water quality, for example, in studies of pollution.
A famous study involving mayflies was conducted in Lake Erie during the 1950s and early 1960s. Lake Erie was badly polluted at that time, especially by organic debris associated with sewage and algal growths, the decomposition of which consumed most of the oxygen in the waters of deeper parts of the lake. The development of anoxic conditions resulted in mass die-offs of nymphs of the mayflies Hexagenia rigida and H. limbata, which were previously extremely abundant. The virtual collapse of these populations was widely reported in the popular press, which interpreted the phenomenon as an indication that the great lake was “dead,” and had been rendered as such by pollution caused by humans. Today, the waters of Lake Erie are much cleaner, and its populations of mayflies have recovered somewhat.
Both nymphal and adult mayflies are a very important food for economically important sportfish, such as trout and salmon. Many sport fishers are highly skilled at tying mayfly “flies” as lures for use in fishing. The more realistically the lure portrays the species of mayfly that the trout or salmon are interested in feeding upon in a particular stream at a particular time, the greater is the fisher’s success in catching fish.
See also Indicator species; Stoneflies.
Resources
BOOKS
Arnett, Ross H. American Insects. New York: CRC Publishing, 2000.
Borror, D. J., C. J. Triplehorn, and N. Johnson. An Introduction to the Study of Insects. New York: Saunders, 1989.
Campbell, I. C., ed. Mayflies and Stoneflies: Life Histories and Biology. New York: Kluwer, 1990.
Carde, Ring, and Vincent H. Resh, eds. Encyclopedia of Insects. San Diego, CA: Academic Press, 2003.
Freedman, B. Environmental Ecology. 2nd ed. San Diego: Academic Press, 1995.
Peckarsky, B. L., et al. Freshwater Macroinvertebrates of Northeastern North America. Ithaca: Cornell University Press, 1990.
OTHER
Ohio State University Extension. “Mayflies” <http://ohioline.osu.edu/hyg-fact/2000/2166.html> (accessed December 3, 2006)
U.S. Geological Survey; Northern Prairie Wildlife Research Center. “Mayflies of the United States” <http://www.npwrc.usgs.gov/resource/distr/insects/mfly/index.htm> (accessed December 2, 2006).
Bill Freedman
Mayflies
Mayflies
Mayflies, or shadflies, are aquatic insects in the order Ephemeroptera. There are several thousand species of mayflies, distributed among 20 families. Mayflies have a relatively protracted nymphal stage, which occurs in freshwater habitats. The adults are a short-lived stage during which dense aggregations of animals engage in a frenzied procreation, needed to perennate the species in its local habitats.
Biology of mayflies
Mayflies have a simple metamorphosis , with three life-history stages: egg, nymph (or naiad), and adult. The nymphal stages are numerous and relatively protracted, generally lasting for at least one year. Mayfly nymphs occur in aquatic habitats, and account for most of the lifespan of mayflies. Some species have as many as 28 nymphal molts. The last, pre-adult stage occurs when a nymph rises to the water surface, molts, and develops into a winged form called a subimago, which flies a short distance, and usually rests on vegetation. Within a day or so, the subimago molts into the terrestrial, sexually mature adult stage, which is generally found in close proximity to the aquatic nymphal habitat . Mayflies are the only insects that have an additional molt after they have developed functional wings.
Mayflies have soft, elongate bodies, with two or (most commonly) three, distinctive, thread-like appendages projecting from the end of their abdomen. Adult mayflies have short antennae and many-veined, roughly triangular, membranous wings. The wings are held erect and together over the body when the animal is at rest, and cannot be folded up as in most other orders of insects. The aquatic mayfly nymphs have distinctive, leaf-shaped appendages on the sides of their abdomen that serve as gills for the exchange of respiratory gases.
Larval mayflies are aquatic in fresh waters, and have mouthparts adapted for feeding on algae and other relatively soft, organic materials. Most mayflies are herbivores or detritivores, but a few species are carnivores of other aquatic invertebrates . Because they do not feed, adult mayflies have only vestigial mouthparts. Mayflies have large, compound eyes, and in many species the males are larger than the females, and have forelegs adapted for grasping the female during the nuptial (mating) flight. In most species the forewings are relatively large, while the hindwings may be absent, or are reduced in size compared with the forewings.
Adult mayflies do not feed and are short-lived, only living for a few hours or several days. This fact is reflected in the Latin root of the scientific name of this group of insects, Ephemeroptera, which refers to the highly ephemeral nature of the adult stage. The sole purpose of adult mayflies is procreation. To achieve this goal, adults of particular species emerge synchronously within a brief period of time . Adult mayflies sometimes occur in spectacularly large aggregations, in which the animals mate and deposit their eggs to water in frenzied swarms, and then die soon afterwards. Most of the mayflies in the swarm are males. The females fly briefly into the swarm, find a mate, and they couple then leave to copulate and lay their eggs.
Ecological and economic importance of mayflies
Sometimes, the mass emergences of adult mayflies can involve extremely large numbers of animals. During the brief times when mayflies are very abundant, some people may view them as a nuisance, because the insects seem to be flying everywhere and can be bothersome because of this, or because their bodies accumulate abundantly on beaches, streets, window screens, and in other places. Rarely, the accumulated biomass of mayfly bodies can represent a traffic hazard, by making roads rather slippery. However, this is quite a rare event, and in general mayflies should not be thought of as a nuisance. Mayflies are rarely abundant enough to be a bother. Almost always, mayflies are a harmless part of the natural world.
Mayfly nymphs are an important component of many freshwater ecosystems. Grazing by mayflies is important in preventing the build-up of a large biomass of aquatic algae and detritus, and in nutrient cycling. Because mayflies can be quite abundant in many habitats, they are an important food for many species of predators.
Mayfly species are rather particular in their choice of habitat, and in their tolerance of environmental conditions, such as the temperature and chemistry of water. Because of their specific habitat requirements, mayfly species are often studied by aquatic ecologists as indicators of water quality, for example, in studies of pollution . A famous study involving mayflies was conducted in Lake Erie during the 1950s and early 1960s. Lake Erie was badly polluted at that time, especially by organic debris associated with sewage and algal growths, the decomposition of which consumed most of the oxygen in the waters of deeper parts of the lake. The development of anoxic conditions resulted in mass die-offs of nymphs of the mayflies Hexagenia rigida and H. limbata, which were previously extremely abundant. The virtual collapse of the populations of mayflies in Lake Erie was widely reported in the popular press, which interpreted the phenomenon as an indication that the great lake was "dead," and had been rendered as such by pollution caused by humans. Today, the waters of Lake Erie are much cleaner, and its populations of mayflies have recovered somewhat.
Both nymphal and adult mayflies are a very important food for economically important sportfish, such as trout and salmon . Many sport fishers are highly skilled at tying mayfly "flies" as lures for use in fishing. The more realistically the lure portrays the species of mayfly that the trout or salmon are interested in feeding upon in a particular stream at a particular time, the greater is the fisher's success in catching fish .
See also Indicator species; Stoneflies.
Resources
books
Arnett, Ross H. American Insects. New York: CRC Publishing, 2000.
Borror, D. J., C. J. Triplehorn, and N. Johnson. An Introduction to the Study of Insects. New York: Saunders, 1989.
Campbell, I. C., ed. Mayflies and Stoneflies: Life Histories andBiology. New York: Kluwer, 1990.
Carde, Ring, and Vincent H. Resh, eds. Encyclopedia of Insects. San Diego, CA: Academic Press, 2003.
Freedman, B. Environmental Ecology. 2nd ed. San Diego: Academic Press, 1995.
Peckarsky, B. L., et al. Freshwater Macroinvertebrates ofNortheastern North America. Ithaca: Cornell University Press, 1990.
Bill Freedman
Mayflies
Mayflies
Order: Ephemeroptera
Life Cycle: incomplete
Three Life Stages: egg-aquatic nymph, and adult cycle which includes two phases: (subimago) dun and (imago stage) spinner
Species: over one thousand
Hatch is over a one to three week period yearly
Mayflies undergo an incomplete metamorphosis, meaning that typically in a one year period they go through three cycles: egg, nymph and adults. Most of the mayfly’s life is spent in the nymphal cycle.
There are four different groups that the mayflies are divided into depending on body type and behavior. These are: burrowers, clingers, crawlers and swimmers. Burrowers have an oval, long-shaped body with fringed gills and very visible tusk-like mandibles. The clinger mayfly has a head wider than the abdomen and a flattened body. Crawlers have a head equal to, or less than, the width of the abdomen and have a slightly flattened body. Along the top margin of the abdomen are forked gills; except for a few species they have no tusk-like mandibles. The round, streamlined body of the swimmer has a head equal to, or less than the width of its abdomen. Swimmers have tails where the edges are fringed with fine hair.
Nymphs grow as they molt 20 to 30 times and their wing pads darken as their wings start to develop. As the mayfly nymphs start to emerge, most of them
swim or drift to the surface and emerge as adult mayflies. Some of the mayfly nymphs emerge under the water and must swim to the surface, or they may crawl out to the shore and hatch.
The adult mayfly goes through 2 phases. The first is a dun and the second phase is commonly called a spinner. The newly hatched adults are called duns and fly to the steam’s foliage after emergence. In this dun phase the adults are unable to mate and have opaque wings. The spinner emerges anywhere from one hour to 3 days after the dun sheds its outer covering. The sexually mature spinners have clear wings and form mating swarms in the air. When a female comes into the swarm she is seized by a male and mating takes place. After mating, the male usually falls spent to the water or ground and the female begins depositing her eggs on the water’s surface or sometimes underneath the water. Then she falls spent, creating a spinner’s fall. Trout enjoy most of the phases of the different 4 groups, having interest in some more than others.