A comparison of the rate of metabolic activity in the solitary and migratory phases of Locusta migratoria

Abstract

The occurrence of locusts in two extreme forms or phases, viz., the phasis gregaria and the phasis solitaria was first envisaged as a theoretical conception by Uvarov (1921). It was subsequently confirmed experimentally by Faure (1932), whose main results have been repeated by other observers. Given suitable temperature, humidity, and food, it is now known to be a comparatively easy matter to induce Locusta migratoria , for example, to develop into either phase. In a few words, individuals reared from the egg in isolation develop evident solitaria characters, whereas those reared collectively in large numbers assume the gregaria, or migratory, phase. The differences that have been described as being characteristic of these two phases are those of behaviour, coloration, and of morphological structure. It may be argued that these very evident differences are likely to be accompanied by others of a physiological nature. With the object of exploring possible physiological differences between the two phases, we have studied the rate of oxygen uptake of all the instars of Locusta migratoria , in both its solitary and migratory forms, using this criterion as an indication of the rate of metabolic activity. 2―Technique Employed A special Barcroft apparatus was devised, with cylindrical bulbs of 5 inches in length, all the ground glass joints being sealed with mercury to prevent any leakage during the course of an experiment. The locusts used were all obtained 3 days after each had moulted and were then starved for 24 hours before the experiment. Every care was taken to use the insects in exactly the same condition, as regards feeding and development, in order to allow of a fair comparison being made.