Insect Life Cycle

    

Metamorphosis and Life Stages

During its life cycle, every aquatic insect goes through a series of changes in its form as it develops from the egg to the adult.  The biological term for this process is "metamorphosis."  These various insect "stages" are critically important to the food chain for the fish that inhabit the same waters as the insect.  Hence, they are of interest to the fly fisher who attempts to imitate these various stages of insect life with flies that suggest to the fish that the "bait" on the end of the line is a "natural" insect.    

There are 2 types of insect metamorphosis:  "Incomplete" & "Complete"

  • "Incomplete" metamorphosis . . . the stages in an incomplete metamorphosis are:

    egg ~ larva ~ subimago ~ adult  (click to enlarge)

egg larva subimago adult
egg
mayfly larva mayfly subimago ("dun") mayfly adult ("imago"/spinner)

insect orders which exhibit incomplete metamorphosis:
mayflies, dragon & damsel flies, stoneflies, water bugs

  • "Complete" metamorphosis . . . the stages in a complete metamorphosis are:

    egg ~ larva ~ pupa ~ adult (click to enlarge)

egg larva pupa adult
egg
caddis larva caddis pupa caddis adult

insect orders which exhibit complete metamorphosis:
|fishflies, spongilla flies, water beetles, caddisflies, caterpillars, midges

Please go back / For a closer look at metamorphosis, compare various insect stages