VCSU Macro-Invertabrate Lab
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Order Ephemeroptera - The Mayflies
Common Burrower larvae Flathead Mayfly larvae Small Minnow Mayfly larvae
The term Ephemeroptera refers to the ephemeral nature of the adults of this group. The adults are very short lived, usually surviving for 24 - 48 hours after emerging from the subimago stage. The larvae, however, can have fairly long lives living in their aquatic environments. For the Ephemeroptera we provide a key to the 10 Families of mayfly larvae found in North Dakota rivers and streams. Some of these are common stream inhabitants that are found throughout the state, others are rather localized. Mayflies are often considered to be good indicators of water quality. However, it should be noted that there is considerable gradation in their ability to tolerate impaired water quality. The Caenidae, for example, are known to tolerate high organic conditions.

General Life cycle - The mayflies spend most of their life as aquatic nymphs. When it is time for them to molt into adults they will transform into a stage called the subimago. This is essentially a larval stage that can fly, rather unique in the insect world. The subimago will emerge from the water, fly to an appropriate resting site and slowly transform into the adult phase. An interesting feature of the emergence of the subimago, usually called a hatch, is that large numbers of that species will all hatch synchronously resulting in large numbers of subimagos and adults being present at once. What initiates these hatches is not thoroughly understood. Since adults are very short lived, it is an advantage to have many of them present at once to ensure mating success. Usually within several days after a hatch the adults have mated, females have laid their eggs, and the adults die.

Identification - One of the main features used in larval diagnosis of mayflies are their gills. They are located on the abdominal segments and have a variety of shapes and orientations. The term gill is appropriate because they are used to gather oxygen from the surrounding water. The orientation and structure of the head, structure of the mouthparts, orientation and structures of the legs, and hairs and spination are other useful characters for identification.

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