Locomotor performance of insects with rudimentary wings
James H. Marden & Melissa G. Kramer
Nature 377, 332-334.
The evolution of flight in insects triggered
an unparalleled radiation and diversification such that flying insects comprise
approximately two thirds of all species1,
yet a gap in the fossil record obscures the origins of wings and flight2.
Among modern insects, stoneflies are morphologically primitive for a number
of flight-related traits, which makes their locomotor behavior and physiology
of particular interest3. Here we show that Allocapnia
vivipara stoneflies utilize a non-flying form of aerodynamic locomotion
that may exemplify a precursor to flight. They raise their wings in response
to wind, thereby sailing across water surfaces, but they are incapable of
flapping. Sailing performance improves steadily with increasing wing
size, and even the smallest wings significantly increase sailing velocity
compared to wingless individuals. Performance during aerial gliding is less
affected by wing size, which suggests that sailing is a more plausible setting
for wing evolution. These results support the recent hypothesis that insect
wings evolved from articulated gill plates of aquatic ancestors through
an intermediate semi-aquatic stage4.
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