size of larvae versus pupa versus adult

Discussion in 'Fly Fishing Entomology' started by James Mello, May 12, 2006.

  1. James Mello

    James Mello Inventor of the "closed eye conjecture"

    Joined:
    Feb 25, 2003
    Messages:
    2,808
    Media:
    8
    Likes Received:
    87
    Location:
    Tacoma
    For insects that go through complete metamorphasis, are their some rules of thumb on the size differential of the (nearly full grown) larvae, versus the pupa, versus the adult? When fishing emergers it's tough to match the correct size to the adults, cause I don't know if it's bigger or smaller. And I really don't feel that just changing flies is a good way to figure out what to do. Does any of you guys/gals out there have good rules of thumb on this?

    -- Cheers
    -- James
     
  2. Taxon

    Taxon Moderator Staff Member

    Joined:
    Aug 22, 2004
    Messages:
    996
    Likes Received:
    134
    Location:
    Mercer Island, WA
    James-

    You should think of their body sizes all being essentially the same. In the last larval instar, the larva seals itself in a puparium and evolves into a pupa, which had to fit within the larval exoskeleton, and it isn't eating, so isn't likely to grow in a week or so. Following this dormant period, the pupa cuts itself out of its puparium, and transitions into an adult.

    However once again, the adult had to fit within the pupa's exoskeleton, so the body won't be any longer than that of the pupa. Having said that, one thing to consider when tying, is the length that the wings of the adult extend beyond the end of it abdomen, which I would estimate to be average nearly 1/2 the body length. But, this should not require using a longer-shanked hook on which to construct the body (head, thorax, and abdomen) of the adult.