BEHAVIOR OF SOME SOIL INSECTS. l8l 



by Shafer ('n) and other workers. Grasshoppers were left in 

 pure carbon dioxide for 15 hours and adults of Passalus cornutus 

 for 24 hours and complete recovery resulted. Large percentages 

 of the carbon dioxide caused violent twisting and movements of 

 the larvae for a few minutes and then they became inactive and 

 sluggish or stupefied. No experiments to determine their re- 

 sistance to carbon dioxide were performed. 



The experiments with the gradients of ammonia showed that 

 the adults were affected by the gas but that they did not always 

 react advantageously to it. The percentages used were probably 

 considerably larger than that ever encountered in nature. Under 

 some conditions of decaying vegetable matter considerable 

 ammonia may, however, be present in the air. 



In general the experiments show that the reactions of the larvae 

 and adults to gradients of evaporation, temperature, and carbon 

 dioxide are similar to what one would expect from a study of 

 their habitat. Adams ('15) in speaking of soil conditions says: 

 'The animals which thrive in the soil are likely to be those which 

 tolerate a large amount of carbon dioxide and are able to use a 

 relatively small amount of oxygen, at least for considerable 

 intervals, as when the soil is wet during prolonged rains. . . . 

 The optimum soil habitat is therefore determined, to a very im- 

 portant degree, by the proper ratio or balance between the amount 

 of available oxygen and the amount of carbon dioxide which can 

 be endured without injury." 



IV. ACKNOWLEDGMENTS AND BIBLIOGRAPHY. 



The writer wishes to express his thanks and appreciation to 

 Professor V. E. Shelford, of the University of Illinois, for his 

 criticism and direction of the work. The equipment was supplied 

 with the University of Illinois Graduate School Funds. Ac- 

 knowledgments are also due Prof. L. A. Harding of the Univer- 

 sity of Illinois Engineering School, for advice regarding air flow 

 measurements. 



Only a few of the more important papers and those containing 

 bibliographies will be listed. 



Adams, Charles C. 



'15 An Ecological Study of Prairie and Forest Invertebrates. Bull. 111. St. 

 Lab. Nat. Hist., Vol. XL, No. n. 



