EFFECTS OF ACCLIMATIZATION AND SEX ON RESPIRATION AND THERMAL RESISTANCE IN TRIBOLIUM (COLEOPTERA:TENEBRIONIDAE)

Abstract

Some effects have been studied of prolonged exposure to nonoptimal temperatures on respiration and thermal resistance in the flour beetle Tribolium confusum Duval.Adult beetles maintained at 18 °C. and 38 °C. for a number of months exhibited changes in the location and form of the temperature–respiration curve compared with that of control insects at 30 °C. Insects from 18 °C. showed increased survival ability at −3 °C., but there was no respiratory compensation during acclimatization. Changes in the sign of respiration–weight regression in the experimental groups was probably related to differences in sensitivity to temperature between lighter and heavier individuals.Control 30° males survived exposure to −3 °C. better than corresponding females. This survival difference at the low temperature was eliminated by prolonged maintenance of the insects at 18 °C. Insects from 18 °C. possessed a higher water content and a lower dry weight than controls. A discussion is presented dealing with the influence of the ratio of active to inactive weight on respiration per unit weight.The temperature–respiration curves were adequately expressed in the double-logarithmic form. The constants in this equation were used comparatively among the different experimental groups.