The Stream Doctor

March 17th, 2003

Email YOUR Questions directly to the Stream Doctor. This is your opportunity to get an experts professional opinion on anything stream related.


Q. I wish to know the entire life cycle of the mayfly. I have also heard the term wiggler and would like to know which stage of cycle this is.

A. Because there are many variations in the life cycle of different mayflies in terms of temperature requirements, unique behavior, etc., I will present here a generalized life cycle which fits most, if not all, mayflies.

We'll start with the eggs, which may be deposited in various ways but eventually become attached to the substrate. Embryonic development within the egg usually takes place in a few weeks prior to hatching into the nymph stage. However, it has been shown that the eggs of some species (often in temperate climates) pass through a diapause stage; this means that the egg remains dormant for several months before hatching. Anyway, when the nymphs hatch, they undergo numerous molts as they grow, called instars. As the nymphs grow and mature, they eventually accrue the necessary number of degree-days for them to emerge. The initial adult stage is called a subimago, which is a winged but sexually immature stage. This is a short stage lasting as little as a couple of minutes or as much as 48 hours. Finally, the subimagos molt again into the sexually mature adults or imagos.

So briefly, the life cycle is egg to nymph to subimago to adult; eggs may pass through a dormant diapause stage and nymphs pass through several instars.

Don't hesitate to contact me if you want more detailed information on mayfly life cycles. I'd be glad to give you some references to publications that go into considerable detail.

The second part of your question pertaining to the name "wiggler" is a bit harder to address. If you heard this term applied to mayflies, then the only life stage that would even fit this description would be the nymphs. Many move by wiggling movements in the water column or among the rocks on the stream bottom. However, the larval stage of mosquitoes (order Diptera) are often referred to as "wigglers," so whoever you heard this from may have been talking about them.

~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584
Email: streamdoctor@aol.com

The 'Stream Doctor' is a retired professional stream ecologist and author, now living in the West and spending way too much time fly-fishing. You are invited to submit questions relating to anything stream related directly to him for use in this Q & A Feature at streamdoctor@aol.com.


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