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Insect metamorphosis is a fascinating and
highly successful biological adaptation, but there is much uncertainty
as to how it evolved. Ancestral insect species did not undergo
metamorphosis and there are still some existing species that
lack metamorphosis or undergo only partial metamorphosis. Based
on endocrine studies and morphological comparisons of the development
of insect species with and without metamorphosis, a novel hypothesis
for the evolution of metamorphosis is proposed. Changes in the
endocrinology of development are central to this hypothesis.
The three stages of the ancestral insect species -- pronymph,
nymph and adult -- are proposed to be equivalent to the larva,
pupa and adult stages of insects with complete metamorphosis.
This proposal has general implications for insect developmental
biology. |
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