Morphology and Flight Control


Flexible wing morphology and secondary control structures

One of our goals in studying how insects perform complex, fitness-related flight behaviors in natural environments is to uncover morphological, physiological or behavioral features that may be under particularly strong selective pressure for improving flight performance in the wild.  Our current understanding of insect flight biomechanics is founded on studies employing dynamically scaled robots, computational models, or highly controlled laboratory preparations, which have provided insight into how flapping wings produce aerodynamic forces, but which involve a number of simplifications.  In addition to limiting behavioral and environmental complexity, many of these approaches focus solely on the gross kinematics of the wings, excluding movements of other body parts, as well as the structural complexity and dynamic shape changes that occur in flexible, flapping insect wings.

The instantaneous shape of flapping wings can have a profound influence on fluid dynamic force production and efficiency.  Insect wings bend and twist dramatically during flight, yet the effects of these passive, three-dimensional shape changes on unsteady aerodynamic force production and flight performance remain largely unknown.  We use a variety of tools - including computational modeling and structural analysis, testing of real and biomimetic wings using at-scale robotics, and in vivo manipulations on freely flying insects – to understand the effects of flexible wing design on flight performance.  Our recent work has focused on comparative studies of the flexible, resilin-filled joints found between supporting wing veins in many insects, and on in vivo manipulations of these joints to alter wing stiffness and assess its effects on performance.  We are also pursuing work as part of the Robobees project (NSF CCF-0926158) in collaboration with the Harvard Microrobotics Laboratory, in which we utilize insect wing designs as the template for artificial wings, and attach artificial and real wings to at-scale robotic flappers to compare force production and fluid flow under controlled conditions.

Another feature of insect flight control that has received relatively little attention is the use of secondary control structures, such as the abdomen and legs, to improve flight stability and control.  We have found that orchid bees extend their hind legs far from their bodies during forward flight in turbulent air, increasing their moment of inertia and reducing rolling instabilities, but also increasing drag and power requirements substantially.  We have also examined how a variety of insects use their abdomen to control body rotations, adjusting abdominal position continuously during flight to slow pitching rotations, in situations ranging from hovering maneuvers to forward flight in unsteady flow.

Related Publications:

Mountcastle, A.M. and Combes, S.A. (2014).  Biomechanical strategies for

    mitigating collision damage in insect wings: structural design versus

    embedded elastic materials.  J. Exp. Biol. 217: 1108-1115.

Mountcastle, A.M. and Combes, S.A. (2013).  Wing flexibility enhances load-

    lifting capacity in bumblebees.  Proc. Roy. Soc. B 280: 20130531.

Donoughe, S., Crall, J.D., Merz, R.A. and Combes, S.A. (2011).  Resilin in

    dragonfly and damselfly wings and its implications for wing flexibility.  J.

    Morph. 272(12): 1409-1421. 

Combes, S.A. (2010).  Materials, structure, and dynamics of insect wings as

    bioinspiration for MAVs.  In Encyclopedia of Aerospace Engineering, Vol. 7

    (Vehicle Design).  John Wiley & Sons, West Sussex, UK.  10 pp.

Shang, J.K., Combes, S.A., Finio, B.M. and Wood, R.J. (2009).  Artificial

    insect wings of diverse morphology for flapping-wing micro air vehicles. 

    Bioinspir. Biomim. 4(3): 036002, 6 pp. 

Combes, S.A. and Dudley, R. (2009).  Turbulence-driven instabilities limit

    insect flight performance.  Proc. Nat. Acad. Sci. US 106(22): 9105-9108.

Combes, S.A. and Daniel, T.L. (2003).  Flexural stiffness in insect wings.  I.    

    Scaling and the influence of wing venation.  J. Exp. Biol. 206(17): 2979-2987.

Combes, S.A. and Daniel, T.L. (2003).  Flexural stiffness in insect wings.  II. 

    Spatial distribution and dynamic wing bending.  J. Exp. Biol. 206(17):    


Combes, S.A. and Daniel, T.L. (2003).  Into thin air: Contributions of    

    aerodynamic and inertial-elastic forces to wing bending in the hawkmoth

     Manduca sexta.  J. Exp. Biol. 206(17): 2999-3006.

Daniel, T.L. and Combes, S.A. (2002).  Flexing wings and fins: bending by

    inertial or fluid-dynamic forces?  Int. Comp. Biol. 42(5): 1044-1049.

Combes, S.A. and Daniel, T.L. (2001). Shape, flapping and flexion: Wing and

    fin design for forward flight.  J. Exp. Biol. 204(12): 2073- 2085.

Press Coverage:

Science magazine, News of the Week, “Frankensteinish Flight of the

    Bumblebee,” v. 339, p. 258, Jan 2013

BBC Four, “Insect Dissection: How Insects Work,” April 2014

Discovery Channel Canada, Daily Planet – Riskin’s Business, “Bee Leash

    episode, 2012

Harvard Magazine, “Bees Knees: Taming Turbulence,” Nov-Dec 2009

Canadian Broadcasting Company, Quirks & Quarks radio program, “The    

    Bees’ Knees,” April 2006