Evolution of and structures involved in wing folding in featherwing beetles (Coleoptera: Ptiliidae).

The ability to fold the wings is an important phenomenon in insect evolution and a feature that attracts the attention of engineers who develop biomimetic technologies. Beetles of the family Ptiliidae (featherwing beetles) are unique among microinsects in their ability to fold their bristled wings under the elytra and unfold them before flight. The folding and unfolding of bristled wings and of the structures involved in these processes varies among ptiliids, but only one species, Acrotrichis sericans, has been analyzed in detail.

Novel flight style and light wings boost flight performance of tiny beetles.

Flight speed is positively correlated with body size in animals. However, miniature featherwing beetles can fly at speeds and accelerations of insects three times their size. Here we show that this performance results from a reduced wing mass and a previously unknown type of wing-motion cycle.

Miniaturization re-establishes symmetry in the wing folding patterns of featherwing beetles.

Most microinsects have feather-like bristled wings, a state known as ptiloptery, but featherwing beetles (family Ptiliidae) are unique among winged microinsects in their ability to fold such wings. An asymmetrical wing folding pattern, found also in the phylogenetically related rove beetles (Staphylinidae), was ancestral for Ptiliidae. Using scanning electron, confocal laser scanning, and optical microscopy, high-speed video recording, and 3D reconstruction, we analyze in detail the symmetrical wing folding pattern and the mechanism of the folding and unfolding of the wings in Acrotrichis sericans (Coleoptera: Ptiliidae) and show how some of the smaller featherwing beetles have reverted to strict symmetry in their wing folding.

Extraordinary flight performance of the smallest beetles.

Size is a key to locomotion. In insects, miniaturization leads to fundamental changes in wing structure and kinematics, making the study of flight in the smallest species important for basic biology and physics, and, potentially, for applied disciplines. However, the flight efficiency of miniature insects has never been studied, and their speed and maneuverability have remained unknown.

The locomotor apparatus of one of the smallest beetles - The thoracic skeletomuscular system of Nephanes titan (Coleoptera, Ptiliidae).

Pterothoracic structures of the minute ptiliid Nephanes titan were examined and described in detail. Effects of miniaturization and the phylogenetic and functional background are discussed. Apomorphies shared with Hydraenidae are the large metascutal shield, the fringe of setae along the posterior edge of the wings, and the fusion of the mesoventrite with the mesanepisternum.

Wing morphology in featherwing beetles (Coleoptera: Ptiliidae): Features associated with miniaturization and functional scaling analysis.

The wings of Ptiliidae, the coleopteran family containing the smallest free-living insects, are analyzed in detail for the first time. A reconstruction of the evolutionary sequence of changes associated with miniaturization is proposed. The wings of several species are described using light microscopy and scanning electron microscopy.