Cuticular Hydrocarbon Differentiation Between Body Parts of Schistocerca gregaria Locusts.

Insects cover their bodies with a layer of cuticular hydrocarbons (CHCs) that reduce water loss and serve as communication signals and potentially as lubricants. CHC composition is highly diverse, varying among individuals and species. However, CHC variation has been rarely studied between different body parts of the same individual. Whether intra-individual CHC variation across the insect body arises from differences in diffusion rates between different CHCs or from distinct functional roles of the CHC layer across body regions remains unknown. Here, we analyzed the CHC composition of antennae, head, thorax, abdomen, front legs, hind femur and tibia, as well as whole-body extracts of the desert locust Schistocerca gregaria subadults using gas chromatography-mass spectrometry (GC–MS). While most body parts were relatively similar in CHC composition, head and antennae were distinct from the others. Both had shorter n-alkanes and more branched alkanes than the other body parts, which should lower the CHCs’ melting temperatures and hence render the CHC layer more fluid. On the antennae, this likely reflects their role as sensory organs in chemical communication, as more fluid CHCs have been suggested to be more easily perceived. We additionally examined the femoro-tibial joint of the hind leg using solid-phase microextraction (SPME). The joint contained fewer and shorter n-alkanes than the femur, indicating a relative enrichment of more fluid CHCs, which may facilitate lubrication. Together, these results show that CHC composition in S. gregaria varies systematically across body regions. This likely reflects that CHCs are optimised for distinct functions in desiccation resistance, chemical communication, and mechanical lubrication, depending on the body part.