The Thermal Resistance of Mayfly Nymphs from Ponds and Streams

Temperature is a factor of great importance in determining the distribution of animals. There are many references in ecological literature to a correlation between distribution of animals and the temperature conditions prevailing in the habitats occupied by the animals. Particular instances of this correlation are the distribution of stream turbellarians (Steinmann, 1906; Thienemann, 1913) and the effects of abnormal temperature conditions on local faunas (Allee, 1923; Stephens, 1938). The great significance of temperature to the animals themselves is shown by the many physiological studies of its action on living matter (Bélehrádek, 1935), and is also evident in the ecologists’ use of the terms stenotherm and eurytherm. This correlation between temperature and distribution has rarely, however, been investi-gated from the experimental standpoint. One line of approach has been the experimental investigation of the thermal resistances of animals from different habitats.