. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 10 12 14 16 18 Air Temperature(°C)=6 + -^ 20 22 + 2TAM). n r M J J A s Month 0 N D FIGURE 5. Light and temperature relationships near Lahaska, Pennsylvania. Left-hand plot (A) shows relationship between mean tree-hole temperature and air temperature. TAt and TAt-i are mean daily air temperatures of the current and previous day, respectively. Miean daily temperatures are calculated as the average of the daily maximum and minimum. Right-hand curves (B) show the seasonal march of both temperature (94-year average) and light (su
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 10 12 14 16 18 Air Temperature(°C)=6 + -^ 20 22 + 2TAM). n r M J J A s Month 0 N D FIGURE 5. Light and temperature relationships near Lahaska, Pennsylvania. Left-hand plot (A) shows relationship between mean tree-hole temperature and air temperature. TAt and TAt-i are mean daily air temperatures of the current and previous day, respectively. Miean daily temperatures are calculated as the average of the daily maximum and minimum. Right-hand curves (B) show the seasonal march of both temperature (94-year average) and light (sunrise to sunset plus one civil twilight) for Philadelphia, Pennsylvania. Temeperatures were taken from the Climatic Atlas of the United States (United States Department of Com- merce, 1968) and daylenghs from Tables of Sunrise, Sunsrt, and Twilight (Nautical Almanac Office, United States' Naval Observatory, 1962). mechanisms involved, an individual committed to resumed development by virtue of its photoperiodic clock will assume a more conservative rate at lower tempera- tures and photoperiods than at higher or longer ones. In terms of rates of development (Fig. 3), chilling increases the responsiveness to all photoperiods. Thus, increased responsiveness to longer days results in a decrease in the depth of diapause; increased responsiveness to shorter and inter- mediate days results in a decrease in the critical photoperiod. Short of evoking the termination of diapause directly, these effects of chilling remain hidden until the larvae subsequently experience photoperiods at temperatures compatible with morphogenesis. It is tempting to draw a parallel between the accumulated facilita- tion of development in T. rntilns and the summation of covert effects of ecdysone in the fleshfly, Sarcophaga peregr'ma (Ohtaki, Milkman, and Williams, 1968). In 5*. peregr'ma, ecdysone is rapidly inactivated, but its effects accumulate so that even though the titer of ecdysone at any one time rem
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
