Variation in the pterostigma of percher and flier dragonflies (Libellulidae)

Insect wings possess morphological adaptations that improve flight aerodynamics, and flight and
wing dynamic studies have implications in mechanical flight design in non-biological systems.
For example, the nodus and characteristically thicker framing veins of dragonfly wings provide
tensile strength and flexibility that likely increase load-bearing capacity and tolerance of
dynamic load conditions. However, the pterostigma of odonate wings has had relatively less
research regarding its role in flight dynamics in dragonflies. The pterostigma is thought to
contribute mass towards the leading edge of the wing to provide stability, regulate wing pitch,
absorb vibration, increase critical flying speed, and reduce the possibility of wing damage during
prolonged and high-speed flight. However, it is unclear how variation in naturally selected flight
behaviors, specifically perching and flying, covary with pterostigma characteristics. Because
perchers and fliers vary in flight demands, we hypothesized that there would be differences in the
qualitative and quantitative characteristics of the pterostigma between the two groups. To assess
morphological differences of the fore- and hindwing pterostigmas between perchers and fliers,
we utilized scanning electron microscopy (SEM) to delineate qualitative differences, as well as
quantitative measurements of the pterostigma and whole wing parameters. We found differences
in both qualitative and quantitative pterostigma characteristics between perchers and fliers,
including a larger, heavier pterostigma in perchers, as well as different visual features between
the two groups’ pterostigmata. These results suggest that differences in flight demands between
perchers and fliers have likely selected for variation in pterostigma characteristics to support
differential flight behaviors.