350 Eelation of Watek to the Behavior of 



closer agreement in temperature readings. A small strip of wire-netting was 

 then fastened around the base of each bell-jar to afford a free circulation of air. 



The environmental conditions produced artificially within each bell-jar were 

 measured in the following manner : Thermometers were suspended in each jar 

 and temperature readings were taken five times daily at 5 and 9 a. m., 1, 5, and 

 9 p. m. ; they show a close agreement of the three jars. The evaporation-rate 

 was obtained by means of a single atmometer placed in each jar, and the cubic 

 centimeters evaporated by this instrument were recorded twice each day at 8 a. m. 

 and 8 p. m. In averaging the different rates, it was found that the moist jar 

 showed an evaporation rate of 14.5 c. c. daily, the medium moist 20.7 c. c, and 

 the dry 25.0 c. c, respectively. The results show that the air temperatures 

 within each jar were approximately uniform during progress of the experiment, 

 and furthermore that the anticipated differences in the rates of evaporation were 

 produced in this manner. Thus the environmental conditions for this test were 

 experimentally attained. 



Sixty beetles of batch 2 were now divided into three groups of 20 each, and 

 on June 20 were distributed to the jars mentioned above. In the jar with a low 

 rate of evaporation the beetles reacted normally in feeding upon the potato 

 plants, and laid eggs on the third day, June 23, but in the jar with the medium 

 evaporation-rate, the animals, though resting upon the plant leaves, laid no 

 eggs for 9 days, or until June 29. In the third jar, with a high rate of evapora- 

 tion, which produced the greatest degree of desiccation, they stayed upon the 

 potato vines for 5 days or until June 25, when they entered the ground and 

 there remained until the summer rains began July 11 ; they emerged, however, 

 from the soil on July 13, and oviposition occurred within 3 days. 



These results showed that egg-production was modified by differences in the 

 evaporating power of the air surrounding these animals, and that a low rate of 

 evaporation, coincident with a high water-content, encouraged oviposition, but 

 that a high rate of evaporation, which reduced their water-content, retarded 

 reproduction. So with a high rate of evaporation the beetles were desiccated ; 

 their tropisms were reversed and they entered the soil, where they remained 

 until their moisture-content was sufficiently increased; they absorbed water 

 until their reactions became normal, when emergence resulted. 



It was shown clearly that reproductive activity occurred during a period of 

 high water-content in the surrounding medium, whether atmosphere or soil, 

 and that desiccation, by reversing the animal's tropisms, inhibited and post- 

 poned reproductive reactions of the L. decemlineata, which is a typical grassland 

 organism. This demonstrated that the introduced stock had adjusted itself to 

 the complex of desert conditions and reacted in the same manner as did the 

 indigenous organisms of the surrounding region. Accordingly, in the majority 

 of species, we should expect reproduction to coincide with the season of high 

 water-content and a dormant period to follow the dry season, regardless of any 

 discovered structural adaptations. 



ROLE OF WATER IN THE PRESERVATION OF LIFE. 



In the desert it was found that hibernating insects could continue life during 

 long dry seasons of one or more years ; therefore, experiments were undertaken 

 to answer the following questions : How was such vitality preserved ? Was this 



