http://royalsociety.org/news/2013/bees-flexible-wings-lift-loads/

New research published today in Proceedings of the Royal Society B
demonstrates that the secret of bumblebees’ capacity for lifting relatively
heavy loads lies in the flexibility of their wings.

A bumblebee with pieces of glitter stiffening its flexible vein joints. ©Andrew
Mountcastle

Harvard University scientists manipulated the wings of live insects to
investigate how wing deformations affected bumblebee aerodynamics. They found
that wing flexibility enhances vertical force production, and thus how much
weight bees can lift while in flight.

Insect wings are flexible structures that passively bend and twist during
flight. Only recently has insect flight research explored the aerodynamic
consequences of flexible wing deformations. However, results from robotic models
have contradicted those of computational models on whether wing deformations
enhance or diminish aerodynamic force production.

Thanks to Peter Bolton.