348 



Relation of Water to the Behavior of 



EXPERIMENTS WITH SOIL MOISTURE. 



It was important to determine the effect of a varying soil-moisture upon 

 oviposition in these organisms during hibernation. Tubes used in experiments 

 upon this subject were 30 cm. long and 15 cm. in diameter, and made of wire 

 netting surrounded by several layers of tinfoil to prevent the egress and ingress 

 of moisture. Three of these tubes were filled with a mixture consisting of equal 

 parts of sand and adobe, and then sunk in a large box of sand, so that only the 

 tops were exposed. The sand in the box was kept damp by means of self- 

 watering automatic soil-cups, which were devised by Hawkins (1910), the 

 purpose of this wet sand being to keep the organisms within the tubes at a 

 uniform temperature, a result attained through rapid evaporation of water- 

 vapor from the surface of the soil. 



The desired differences in soil-moisture were produced in the above tubes in 

 the following manner: In one tube were placed two porous soil-cups, which 

 gave the soil a high water-content ; in the second one, however, a small porous 

 soil-cup was placed, which kept the soil -within at a lower moisture than in the 

 former; and in the third, no soil-cup was employed, thus keeping the soil dry. 

 It was thus possible to obtain differences in soil moisture with other conditions 

 approximately uniform. But to make certain that the above apparatus produced 

 the desired results, determinations of soil-moisture within these tubes were 

 made every second day throughout the experiment. These data are tabulated 

 in Table 3, which shows that the moist soil contained 15.8 per cent moisture, 

 the medium moist soil 8.8 per cent moisture, and the dry soil 1.9 per cent 

 moisture. Thermometers were placed in these tubes at a depth of 15 cm. and 

 readings were made at 5 and 9 a. m. and at 1, 5, and 9 p. m. When tabulated, 

 these soil temperatures throughout the test indicated a close agreement for all 

 experimental tubes. 



Table 3. 



The 60 beetles of batch 1 were now divided into three groups, and when 

 tested in the constant-temperature chamber were found to react positively to 

 light and negatively to gravity. Each group was now weighed, group A weigh- 

 ing 3.3-41 grams, group B, 3.329 grams, and group C, 3.337 grams, respectively. 

 Each group was next buried on June 19 at a depth of 15 cm. in each of the three 

 experimental tubes as indicated, members of A being buried in a moist tube, 

 those of B in one less moist, and those of group C in a dry tube. These animals 

 remained as buried until June 27, 6 p. m., when their weights were again tested 

 in the constant-temperature room, and group A was found to weigh 3.213 grams, 

 group B 2.962 grams, and group C 2.107 grams, respectively. 



