The Stream Doctor

May 12th, 2003

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

Q. Why do some aquatic insects need a pupal stage to become adults and others don't? This may be a "why is the sky blue, daddy?" type question, but I have always been amazed at how many ways nature accomplishes the same task with different processes.

A. Recent research in this field has determined that the main purpose of the pupal state in insect development is to provide those insects that do not have external wing pads a stage in their development where the wings can develop outside the body. A second part of the pupal development then allows the wing muscles to develop within the thorax of the insect's body. Dr. Bruce Wallace of the University of Georgia helped me with this information.

Some signficance has been place upon the evolutionary aspects of the amount of food provided by the size of the egg in determining whether a pupal stage is necessary. However, this has largely been discounted as the major purpose of the pupal stage.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584

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

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