|
Insect Morphology and SystematicsInsect Morphology and SystematicsIncomplete Metamorphosis
A more extensive form of metamorphosis is termed incomplete or abrupt
metamorphosis. Insects that use this mode of development pass through several nymphal
stages before the nymph molts to the winged adult. These insects are usually aquatic with
external gills. At the beginning of life, insects that undergo incomplete metamorphosis, such as
aquatic dragonfly and damselfly (Orthopterans) nymphs, called naiads, go through a molting
process similar to gradual metamorphosis. These insects have six legs, a head with compound
eyes and antennae, and a small abdomen with gills at the posterior end. The head becomes
proportionately smaller and the abdomen larger with successive molts. As they approach
adulthood, wings appear on the back, much as they do if the animal were to undergo gradual
metamorphosis.
As these insects metamorphose, the insect abruptly changes its body form. The gills are
lost and wings develop. But the changes in leg form, head shape, abdominal morphology,
development of spiracles for air breathing, and reduction in the size of mouth parts, drastically
alter the appearance of the insect. Looking at the penultimate naiad and the adult, most naive
observers would not guess they were related
– never mind being the same individual.
Dostları ilə paylaş: |
|
|