Locusts use a composite of resilin and hard cuticle as an energy store for jumping and kicking

To jump as quickly as they do, insects use specialized spring-loaded structures to store and release large amounts of mechanical energy. To store this mechanical energy, the locust uses a structure composed of a layer of a soft protein called ‘resilin’ and a layer of hardened insect cuticle. This layering is similar to the construction of a composite bow.

HFSP Cross-Disciplinary Fellow Gregory Sutton and colleagues
authored on Thu, 27 September 2012

There are many insects that are famous for jumping quickly.  Jumping at these speeds requires using intricate anatomical ‘springs’ to slowly store and then quickly release mechanical energy - energy that can be used to generate escape jumps or energy that can be used to propel powerful kicks to defend the insect from predators.  It was previously thought that these anatomical springs could be grouped into two basic categories based on their composition.  The first category was exemplified by the springs used by fleas, which were thought to be made of a highly elastic protein called ‘resilin’ (Bennet-Clark and Lucey (1967); Rothschild and Schlien (1975)).  The second category was exemplified by the springs used by locusts, which were thought to be made of hard insect cuticle (Bennet Clark (1975)).  This categorization was called into question by the discovery that the fastest of the jumping insects, the froghopper, had an anatomical spring that combined both resilin and insect cuticle into a two-layered composite structure similar to the construction of a composite bow (Burrows et al. 2010).  Was it possible that the froghopper, due to its fast speed, had evolved a uniquely intricate spring, or was this a sign that something had been missed in the analysis of other insect springs?

Figure: A: photo of the outside of the semi-lunar processs in normal and UV light, showing hard black cuticle (marked by black arrows), and the fluorescing blue resilin (marked by yellow arrows).  B: photo of the inside of the semi-lunar process showing the layering of the hard black cuticle and the resilin.  C: photo of the cross section of the semi-lunar process showing the layering of the hard black cuticle and the resilin. D: anatomical sketch of the hindmost leg of a locust with the semi-lunar process shown in the red box.

Burrows and Sutton revisited the anatomical spring of the locust, which is a structure in both hindmost legs called the ‘Semi-Lunar process’, or ‘SLP’, for short.  Because the hardened black cuticle of the SLP is easily seen by the naked eye, it was thought that the SLP was made entirely of hardened black cuticle.  Burrows and Sutton found that, when illuminated by ultra-violet light, small portions of the SLP shone a bright blue colour – a trademark of the protein, ‘resilin’.  Moreover, when the locust deforms this spring to store energy, both the fluorescing section and the hard cuticular section were deformed.

Burrows and Sutton then looked deeper in to the SLP by cutting it transversely to look at the cross section of the anatomical spring (Figure 1).  The transverse sections revealed two layers of material: one made of hardened black cuticle, the other made of the elastic protein resilin.  The locust, like the froghopper, had an anatomical spring that was made of a layered composite, similar to the layered composite structure of an archer’s bow.  This suggests a general principle: insects use a composite bow-like structure to store and release mechanical energy. These intricate biological springs represent an evolved system that parallels, and may represent improvements to the spring technologies employed today.

Reference

Locusts use a composite of resilin and hard cuticle as an energy store for jumping and kicking. Burrows, M. and Sutton, GP. (2012). J. Exp. Biol. 215,pp 3501-3512. doi: 10.1242/​jeb.071993.

Other References

The jump of the flea: a study of the energetics and a model of the mechanism. Bennet-Clark, H. C. and Lucey, E. C. A.(1967).  J. Exp. Biol. 47, 59-76.

The jumping mechanism of Xenopsylla cheopis. Exoskeletal structures and musculature. Rothschild, M. and Schlein, J.(1975).  Philos. Trans. Roy. Soc. Lond. B. 271, 457-490.

The energetics of the jump of the locust Schistocerca gregaria.  Bennet-Clark, H. C.(1975). J. Exp. Biol. 63, 53-83.

Resilin and cuticle form a composite structure for energy storage in jumping by froghopper insects. Burrows, M., Shaw, S. R. and Sutton, G. P.(2008). BMC Biol. 6, 41.

Pubmed link

How fleas generate their famous jumps (another Awardees' Article by Gregory Sutton)