. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 86 D. G. R. McLEOD AND STANLEY D. BECK the maximum temperature took one hour. The performance of the temperature- controlling apparatus was verified by a recording thermograph. Throughout this paper the term short-day refers to a photoperiod consisting of 13 hours of photophase and 11 hours of scotophase, and the term long-day refers to a photoperiod with a 16!-hour photophase and a 7^-hour scotophase. These experi- mental conditions were employed because previous work had shown that over 90% incidence of diapause was induce
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 86 D. G. R. McLEOD AND STANLEY D. BECK the maximum temperature took one hour. The performance of the temperature- controlling apparatus was verified by a recording thermograph. Throughout this paper the term short-day refers to a photoperiod consisting of 13 hours of photophase and 11 hours of scotophase, and the term long-day refers to a photoperiod with a 16!-hour photophase and a 7^-hour scotophase. These experi- mental conditions were employed because previous work had shown that over 90% incidence of diapause was induced in the Madison population of the European corn borer when they were grown under a 12-13-hour photophase in a 24-hour photo- period. Either more or less light induced less diapause. There was no appreciable (D cr LJ a .8 .6 NON DIAPAUSE. DIAPAUSE _L 10 14 18 22 26 LARVAL AGE IN DAYS 30 34 FIGURE 1. Rate of oxygen consumption by diapause and nondiapause larvae of the European corn borer. diapause in response to a long day, continuous light, or continuous dark (Beck and Hanec, 1960). Diapause in the individual borer was determined by a negative criterion—fail- ure to pupate. With such a criterion, there had to be an arbitrary point of time selected, after which the borers were considered to be in diapause. This point was reached experimentally when the control borers, reared in the dark, had finished pupating and the pupation curve for the experimental population had leveled off (see Figure 2). Diapause borers were obtained for experimentation by rearing them in a short day for 21 days after eclosion. At this time they were placed in clean vials on wet paper strips. Experiments on breaking diapause were terminated when all the borers in the sample had either pupated or Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectl
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