RESPONSES OF YOUNG TOADS TO LIGHT 

 AND CONTACT 1 



C. F. CURTIS 'RILEY 



One figure 



CONTENTS Page 



I. Introduction 179 



II. Response to Intense Artificial Light 180 



III. Response to Less Intense Artificial Light 184 



IV. Response to Strong Diffuse Daylight 186 



V. Response to Weak Diffuse Daylight 189 



VI. Response to Sunlight 191 



VII. Response to Colored Light 193 



VIII. Response to Contact 198 



IX. Discussion 205 



X. Summary 210 



XL Bibliography 213 



I. INTRODUCTION 



Several years ago the opportunity arose to investigate the 

 responses of a number of young toads, Bufo americanus Le 

 Conte. 2 The toads averaged about 14 mm. in length. The 

 animals were kept in a glass aquarium jar in the laboratory, 

 the vessel being placed 3 m. from an east window in a shaded 

 place. A piece of filter paper, dampened with water, was placed 

 in the bottom of the jar in order to keep the animals moist. 

 They were fed each day on small flies and mosquitoes. 



As the toads displayed marked responses to light and contact, 

 it was decided to commence experimentation with photic and con- 

 tact stimuli. The entire series of experiments were carried on in a 

 dark room at an approximate temperature of 22 C. For experi- 

 mental purposes, a glass dish with parallel sides was used. The 

 dimensions of the vessel were 60 x 2 5 x 6 cm., inside measurements . 

 In order to eliminate the effects of reflection, the experimentation 

 trough was painted a dull black on the inside with the excep- 

 tion of the two ends ; each of which was covered with a strip 



Contributions from the Zoological Laboratory, University of Illinois, under the 

 direction of Henry B. Ward, No. 21. 



2 The experimental work was done at Ann Arbor, Michigan, in the summer of 

 1904, and the first draft of the paper was made the following year. The literature 

 was reviewed, the paper recast and entirely rewritten at Urbana, Illinois, during 

 the winter of 1912-1913. 



179 



