354 Eelation" of Water to the Behavioe of 



400 of these were sifted from the soil and buried in the adobe and sand portions 

 of the two plots, after having been placed in tubes as in previous tests. On 

 May 1, when 4 tubes from these plots were examined, it was found that the tube 

 from adobe in the covered shelter showed 49 living beetles, while the one from 

 sand contained only 4; on the other hand, the tube from the adobe portion of 

 the open plot was found to have 47 living insects, and those from sand 39. On 

 October 1, when the remaining 4 tubes were removed, those in adobe from the 

 sheltered plot contained 46 live animals, but those in the sand none ; those from 

 the open plot contained no individuals which had hibernated successfully. This 

 natural type exhibited the greatest resistance because of the large number of 

 survivals, and it also appeared that adobe was more favorable to the main- 

 tenance of life than was sand. 



In Table 4 the results are briefly indicated; it is shown there that insects 

 with all activities normal die when buried, for no beetles were found under any 

 of these conditions. It appears also that either the summer or winter genera- 

 tion may be buried and still live, providing the animals were desiccated previous 

 to burial. It is also shown that a covered plot with adobe soil is a most favor- 

 able condition for the preservation of life. It is also demonstrated that insects 

 can be desiccated at any time, when they will burrow into the ground, and may 

 remain there many months without apparent injury. These tests further show 

 that the large pores in sand permitted too rapid drying, so that the animals were 

 desiccated beyond recovery. Livingston (1910) shows that this adobe soil has 

 a water-holding power twice as great as sand, which agrees with the above results 

 and explains why these insects continued to live. Lastly, since the adobe soil in 

 an arid region does contain such a high percentage of moisture, it therefore 

 is the best medium for the sustentation of desert life. 



RELATION OF WATER LOSS IN INSECTS WHEN EXPOSED TO 

 CHANGES IN THE RELATIVE HUMIDITY OF THE SUR- 

 ROUNDING MEDIUM AND ITS EFFECT ON THE ACTIVITIES 

 OF SUCH ORGANISMS. 



The relation of water-loss, i. e., transpiration and respiration from exposed 

 surfaces, to the behavior of plants and animals has already received some atten- 

 tion. This is especially true of plants, the water-relations of which have been 

 studied by Livingston (1906), Lloyd (1912), MacDougal (1912), Eenner 

 (1910, 1911), and other plant physiologists. The results of Livingston (1906) 

 are of interest in this connection, since they show that there is a close relation 

 between the daily march of evaporation, as measured by the atmometer, and 

 transpiration in plants. The following experiments upon insects show that 

 these animals exhibit a physiological behavior not unlike that of transpiration 

 in plants, but the results further show that tropisms of insects are modified by 

 loss of water, which in turn is governed by the evaporating power of the air. 

 There is wide literature upon perspiration, but it does not bear directly upon 

 our problem ; accordingly we shall consider such researches as have been made 

 upon transpiration and evaporation and the efficiency of these processes in 

 modifying behavior. 



The results which follow upon the behavior of insects and other desert animals 

 and upon the relation of evaporation to their behavior and life economy was 



