From CreationWiki, the encyclopedia of creation science
Mayflies are any of the species of flies that belong to the taxonomic Family Ephemeroptera. The mayfly is well known for being a very small fly, but its also known as the "one day fly". The word Ephemeroptera basically means short lived and with wings. The mayfly is a short living animal and can live for up to three hours. Mayflies are aquatic animals that have amazing wings to fly with. The baby stage is called a nymph and the adult stage is very short lived. There are about 2,500 species known world wide of the mayfly. All of them uniquely different and showing their own characteristics. 
The Mayfly anatomy consists of three main body parts; head, thorax, and Abdomen. It also has two wings and three legs. Their fore wing and hind wing, and their fore, leg middle leg and hind leg. When they are nymphs they start out with all of that except the wings with two compound eyes. The eyes are located on the top or side of head and usually bigger in the males. They also have short antennas as nymphs but will grow bigger when older. The legs contain multiple bones and spines. With the abdomen containing spines and tubercles the thorax contains the wing pad, were later the wings develop and grow. The natural shape of the mayfly helps with identification and species. They also have gills which range in shape and size and are located on the lateral or dorsal side.
The adult mayfly has similarities between the nymph but some big differences. Like the males can change the color of their eye and they have two antennas. Strangely the mayflies mouth is useless for eating. The main reason for male mayflies is to reproduce, so they really don't have time to do anything else. The adults have delicate wings though when they grow. Most of them have two pairs of wings. It is easy for a mayfly to fly because their veins are hollow. However they do contain trachea, nerves, and blood. The females have one more body part then the males to help them reproduce. Which helps the female a lot, but the males legs help the male for mating the female. 
Before the process of mating for mayflies the males take part in a giant flight. All the males go and swarm up below the females. The location, time, flight pattern, and number of mayflies depend on the different species and families. Some swarms have a limited number of males, so there is only limited number of mating that season. So the females have to fly above the males to get ready to reproduce.  After the mayflies mate the females lay their eggs. The females lay them on the rivers surface and then they sink down to the bottom. Then 45 days later they hatch into larvae and get into colonies consisting of 400. After three years they break to the surface of the water. then the females molt once and the males shed twice. They then go into sub adult stage and grow into adult. But sadly they only live several hours after being born. The eggs are then laid by the female dipping her abdomen into the water. Some of the females though will actually go underneath the water to lay her eggs or go to a rock or tree. When the female lays her eggs she usually lays 500 to 3000 eggs. Depending on the species and environment the eggs could hatch in 11 hours or take all the way up to 11 months. Then when it is born it is very small and has little legs and arms. 
The Mayfly start out in a aquatic stage when they are born. So they need a clean and calm environment to mature and grow into larger stages.  When the Mayflies are nymphs they start to feed off bacteria as they move and graze over weeds or rocks. Then when they become adults they become scrapers. Most of them are opportunistic generalists eating whatever they can eat. They usually like dead bacteria called detritus and eat all they can because of there short life spans.  The mayfly nymphs are then eaten by fishes animals and carnivores. Then when they grow wings they get eaten by other, bigger animals. Then when at rest the mayflies are eaten by spiders and big birds. When the females are in the stage of laying their eggs they are very venerable to be eaten to. 
Sometimes the Mayfly is called a one-day fly because of there very short life span. Usually the average mayfly will live from 30 minutes to a whole day depending on the species. Then main reason for the mayfly is to reproduce and swarm over the females to make more babies. When they get all of the mayflies together they perform a dance. They all are born in one area then swarm over an entire lake covering almost all of it. People usually call it Tisza blooming and some people like to catch and eat the mayflies.  Some species will even emerge, reproduce, and die in a single day. The basic life for most male mayflies is two grab and female and reproduce. During flight the male has to fight for a female and try to reproduce. After that the males life is basically over or he dies. 
- Mayflies: Ephemeroptera - Behavior And Reproduction Unknown author, Animal Life Resource, Access November 17, 2010.
- With just hours to live, these swarming insects on Hungary's Tisza River have only one thing on their minds. József L. Szentpéteri, National Geographic, Access November 28, 2010.
- General EcologyUnknown author, Fresh Water Life, Tue Dec 14:08:25.
- Ephemeroptera Arghavan Salles, biology 1B project, 4 August 2000.
- Mayfly Unknown author, Encyclopedia Britannica , access Dec 9 2010.
- Mayfly Unknown author, Wikipedia, 4 December 2010 at 02:01.
- Mayflies (Ephemeroptera) Mr Gordon Ramel, publisher, Access 12/9/10.
- Basic Mayfly Anatomy Eugene P. Macri Jr., The Ultimate Fly fishing publication,Access 12/9/10.
- EPHEMEROPTERA John R. Meyer, Department of Entomology, 5 March 2005.