Decoupling of upper and lower lethal limits

The apparent decoupling of thermal limits in insects is of interest because it is unusual, at least by the standards of marine species. In many of these organisms, upper and lower lethal tolerances vary in synchrony. Before discussing this issue in detail it is worth pausing to determine just what is meant by coupled or correlated responses. Huey and Kingsolver (1993) argued that if selection results in a shift of the entire performance curve (Fig. 6.1), then performance at high and low...

Metabolic rate variation size

Discontinuous gas exchange in ticks is thought to be one of the ways in which these animals maintain the very low metabolic rates required by their sit-and-wait strategy, which includes long periods of fasting (Lighton and Fielden 1995). Scorpions are also thought to have uncharacteristically low metabolic rates, and this has prompted considerable speculation regarding the benefits of low metabolic rates in both groups (Lighton et al. 2001). In turn, this speculation has raised the question of...

Water balance physiology

Most of the recent work has been concerned with the exploration of particular mechanisms, and there is now both a need and an opportunity to take a wider view and attempt to synthesise such knowledge into an understanding of water balance in whole animals in natural situations. Water availability and temperature are the two most important abiotic variables influencing the distribution and abundance of insects, although they are continuously modified by two other major climatic factors, solar...

Metabolism and gas exchange

The concept that insect respiration depends only on diffusion supplemented in larger species by ventilation is in need of an overhaul the situation is much more complex. Insects, like all living organisms, are far-from-equilibrium, dissipative structures. That is, they actively take up energy and nutrients and in doing so alter both themselves and their surrounding environment. Initially, the changes in both directions might appear insignificant, but on a longer time scale their impact can be...

Discontinuous gas exchange cycles

Gaseous Exchange Cycle

Discontinuous gas exchange cycles DGCs are one of the most striking gas exchange patterns shown by insects. Discontinuous gas exchange was originally described in adult insects Punt et al. 1957 Wilkins 1960 , but it was the investigation of DGCs in diapausing saturniid pupae by Schneiderman and his colleagues e.g. Schneiderman 1960 Levy and Schneiderman 1966a,b Schneiderman and Schechter 1966 that resulted in a comprehensive understanding both of the pattern and the mechanisms underlying it....