Dragonfly wings are characterized by a series of veins and cross-veins. One function of the cross-veins is to halt the propagation of tears in the wing membrane. Another function is to control the degree of rotation and wing deformation during the wing beat. The joints where 2 veins meet can have a variety of structures and properties. A joint can be rigid, the fusion of hard surfaces that increases the stiffness of the wing, greatly limiting rotation and deformation. Another type of joint can be flexible with the veins joined by a resilin patch. The resilin is flexible and allows rotation of a cross vein relative to the joint when force is applied. The resilin can also relieve some of the stress experienced by the joint and neighboring membrane. Sections of wing with these resilin patch joints will experience more deformation. Resilin patch joints can be accompanied by spikes on the joint. These spikes limit the amount the joint can rotate.
The many joints and cross-veins allow the wing to flex in a complex manner that can give better flight control and make flight more efficient. At present we have a superficial understanding of how the joints work together to provide wing control. A fuller understanding will require much more measurement and more complex models of wing movement.
Rajabi H, Ghoroubi N, Darvizeh A, Appel E, Gorb SN. 2016 Effects of multiple vein microjoints on the mechanical behaviour of dragonfly wings: Numerical modelling. R. Soc. open sci. 3: 150610. http://dx.doi.org/10.1098/rsos.150610