Mechanical hysteresis of insect cuticles

Solid cuticles exhibit cyclic-hardening whereas intersegmental membranes undergo stress-softening on tensile mechanical hysteresis. These differences are related to the arrangement of chitin microfibrils with respect to direction of the applied load and to the nature and extent of matrix stabilization. It is suggested that cyclic-hardening provides a fine control for intra-instar larval growth in some caterpillars. In addition, it may also provide skeletal regidity on ecdysis before completion of bulk tanning of the presumptive exocuticle in more typical examples of solid cuticle.