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For educational purposes:--

Information on the basics of Entomology

 

Introduction                                                                                                                                                                                                                                                                    Contents

 

An Introduction To The Study of Entomology 1

Kingdom:  Animalia, Phylum: Arthropoda

Subphylum: Hexapoda: Class: Insecta: Order: Ephemeroptera

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Insecta:  Pteragota:  Hemimetabola

  Order: Ephemeroptera (mayflies)

                  (10 Families)

General Summary

Life Cycle

Economic Importance

Sample Examinations

   References      Citations

 

          The Hemimetabola include the Insect orders Ephemeroptera, Odonata and Plecoptera.  These three groups do not have continuous phylgenetic continuity.  Immature stages are called "naiads" that contrasts to the "nymphs" of other forms.  Their wings are net-veined and all have a very high potential for reproduction.  They are a primary source of food for fish in freshwater habitats.

 

General Summary of Ephemeroptera

 

          The term "ephemerida" refers to the short length of adult live, which is rarely exceeds one day.  These insects appear in tremendous numbers, emerging all at once in any given locality.  They are very prominent around Green Bay, Wisconsin where they pile up on bridges, roads, etc., causing great annoyance.


          Adults have v
estigial mouthparts that have been reduced from the biting type, and therefore they do not feed.  Their wings are membranous with a reticulate venation; the posterior pair being very small.  Their caudal filament and cerci are very long.  Metamorphosis is hemimetabolous. The nymphs are aquatic and an active winged stage known as the subimago occurs before the last molt yields an adult.

 

          Life Cycle. -- The eggs are laid in water, scattered over the surface or attached to submerged stones, etc.  Adult females actually enter the water in order to lay their eggs.  One female may lay 4,000 to 5,000 eggs.  Figure ent46 shows graphically the respective lengths of the different developmental stages.

 


        The naiads at first possess no gills but
subsequent instars bare on the abdomen movable paired tracheal gills, which may be branched or lamellate, exposed or protected in a branchial chamber.   Each gill is bladder-like or feather-like and tracheal trunks ramify out into them.  They are very efficient in obtaining oxygen from the water.  The gills are lost before the adult stage is reached. 

 

          The body form varies with the habits. Thus inhabitants of fast-flowing streams have flattened bodies with legs provided with strong clinging claws, e.g. Ecdyonurus. Those, which live in clear still water, have a sleek form for rapid movement, e.g. Chloeon, while burrowing types have fossorial legs, e.g. Ephemera, and are in some forms provided with protective gill operculae, e.g. Caenis. The mouthparts are of the biting type, and the two-jointed mandibles and well-developed superlinguae are features of importance. The nymphs are essentially herbivorous feeding on vegetable matter.  Nymphal life is usually of long duration: as many as twenty-three instars may occur. In order to emerge, the fully fed nymph creeps out of the water on to a plant stem. A molt gives rise to the winged subimago stage.  The subimago flies away and after a period that varies, according to the species, from a few minutes to about 24-hrs.  A second skin (shroud) is cast for the final molt, which yields the short-lived adult. 

 

          In the adult the mouthparts are vestigial, no feeding is done, and the alimentary canal serves no longer for digestion.  Adult males swarm and the females fly into the swarm to mate.  Both sexes have short, feeler-like antennae, a 10-segmented abdomen and two or three long cerci.  Compound eyes are present.  The genital openings are paired with no common oviduct.

 

          Economic Importance. -- Economically these insects are of importance because they constitute a proportion of the food of freshwater fishes, the adults being caught by fish during the mayflies' nuptial dance, and the nymphs being devoured by bottom-feeding fish.  In Wisconsin a separate Mayfly Abatement District was created to control mayflies.  When these insects congregate in large numbers they may cause considerable annoyance to humans and animals when they pile up on bridges, roads, etc.  Some economic damage to structures can occur from dead individuals adhering to surfaces.

 

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Details of Insect Taxonomic Groups

 

          Examples of beneficial species occur in almost every insect order, and considerable information on morphology and habits has been assembled.  Therefore, the principal groups of insect parasitoids and predators provide details that refer to the entire class Insecta.  These details are available at <taxnames.htm>.

 

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References

 

Introduction                                                                                                                                                                                                                                                                           Contents