Grasshopper populations and weather: the effects of insolation on Chorthippus brunneus

ABSTRACT. 1 In nature, the internal body temperature of Chorthippus brunneus Thunberg is found to be raised substantially under the influence of direct insolation. 2 In the laboratory, similarly raised body temperatures, resulting from the radiant heat of a light bulb, lead to a 5.6-fold increase in the rate of development, and a similar or even higher increase in the rate of adult maturation. The rate of egg-production is even more greatly affected, being negligible in the absence of a radiant-heat source. 3 These physiological results provide an explanation for the frequently found correlation between grasshopper abundance and hot and/or dry weather. 4 The results are also discussed in terms of the problems they pose for the derivation of a physiological time-scale for basking insects, and the evolutionary forces and constraints that might give rise to them.