J 83 



older, and more ^table ol" the two : a SCCOnd- 



i;dlc variety in only, as a rule, 



Fids much to thermal influence-. \Vei>mann argued that, in addi- 

 tion to the dim I effect of temperature, alternative inherit, 

 plays an important part in the production < He 



tried to show, moreover, t hat eat I I variety i^ < olored in a<i 



lion to its particular environment and that thi\ adaptation n 

 been brought about by natural selection though he did not succeed 

 in this respect. 



In several instances, local varieties have been artilnially produced 



^ults of t t-ni pi-rat urc control. Thus Standfuss produced in Ger- 

 many, by the application of cold, individuals of Vanessa urtica which 

 we're indistinguishable from the northern variety polaris; and from 

 pupa- of Vanessa carditi, by warmth, a very pale form like that found in 

 the tropics; and, by cold, a dark variety similar to one found in Lapland. 

 Shelford, by subjecting a pupa of a tiger beetle, C. tranquebarica 

 d'ulgiiris) to cold moist conditions (mean temperature, 12 C.; moist) 

 obtained, in Chicago, a color variety like one that occurs naturally in 

 the eastern mountains. 



In a second instance, both pattern and color were modified by hot 

 dry conditions (mean temperature, 37 C.; dry), and a variety obtained 

 such as occurs in the western states. 



In a third experiment, both pattern and color were modified by hot 

 wet conditions (37 C.; moist), and a variety produced like one in the 

 moist southern states. 



These investigators and others, notably Merrifield and Fischer, have 

 accumulated a considerable mass of experimental evidence, the inter- 

 pretation of which is in many respects difficult, involving as it does, not 

 merely the direct effect of temperature upon the organism, but also deep 



ions of heredity, including reversion, individual variation, and the 

 inheritance of acquired characters. 



The seasonal increase in size that is noticeable, as in C. pscudargiolus 

 and /. (//</.v, is doubtless an expression of increasing metabolism due to 



'-ing temperature. Warmth, as is well known, stimulates growth, 

 and cold has a dwarfing effect. While this is true as a rule, there are 

 some apparent exceptions, however. Thus Standfuss found that some 

 caterpillars were so much stimulated by unusual warmth that t hex- 

 pupa ted before they were sufficiently fed, and gave, therefore, under- 

 si/ed imagines. A moderate degree of warmth, however, undoubtedly 

 hastens growth. 



