Figure 4.2 Lipid melting temperatures for cuticle of the grasshopper Melanoplus sanguinipes, measured by infrared spectroscopy. (a) At the melting temperature (Tm) the lipids are 50% melted, as calculated from the fitted logistic curve. (b) Intraspecific variation in melting points and transition temperatures measured using the same individuals. Solid line is line of equality.

Source: Reprinted from Journal of Insect Physiology, 48, Gibbs, 391-400, © 2002, with permission from Elsevier.

afternoon temperatures approaching 50°C, but its body temperature remains significantly below ambient, owing to extremely high rates of cuticular water loss. This does not involve changes in epi-cuticular lipids, but is an energy-dependent process occurring via large pores on the dorsal surface (Toolson 1987; Hadley et al. 1989). It is also possible for evaporative cooling to occur via the respiratory system in desert grasshoppers (Prange 1990), but this is an emergency mechanism and respiratory water loss is normally minimized, as in insects in general.

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