372 Relation" of Water to the Behaviok of 



showed an average of less than 4 per cent water of their dry weights. This 

 was during the dry season, when no beetles had emerged from hibernation up 

 to the above date, but on July 1, the day following, 0.98 inch of rain fell; 73 

 beetles emerged on July 2, and by July 3 eggs were laid. This sharp response in 

 behavior must be attributed to the water-content of the soil, for the beetles 

 emerged immediately after the first rain and oviposition took place within 

 48 hours. The insects of the surrounding desert showed a similar response, 

 inasmuch as the adobe soil held them imprisoned until the first rain, which 

 raised their water-content and softened the soil so that emergence of immense 

 numbers occurred. 



The following experiment was performed to show the relation of physical 

 composition of soils to mortality during hibernation. Three hibernating cages 

 were prepared containing soils, one was composed of sand, another of adobe, and 

 a third of equal parts of sand and adobe. On October 1, 500 hibernating adults 

 were caused to hibernate artificially in each tube by placing the insects at a 

 depth of 40 cm. in the soil, and the soil within each tube was kept slightly moist 

 until late in October; they were then allowed to remain out-of-doors under 

 natural conditions during the winter until May 1, when water was added to each 

 cage. On May 3, 363 adults emerged from the soil mixture, 251 from the adobe, 

 but none from the sand. On May 5, the soil of each cage was sifted, when it 

 was found that all in the pure sand were dead but that only 27 in the adobe 

 and 23 in the soil mixture had succumbed. It appeared, then, that there was a 

 relation between soil composition and mortality during hibernation, for the 

 sand permitted excessive desiccation to occur, the adobe and mixed soils did 

 not admit of great desiccation, but most individuals were hibernated suc- 

 cessfully in the mixture of equal parts of adobe and sand. 



EMERGENCE FROM HIBERNATION. 



The physiological complex of emerging beetles was next considered in refer- 

 ence to two phases of the problem. In one case the reactions of hibernating 

 beetles caused to emerge by applying water to the soil were determined, and in 

 the other the reactions of similar adults, in which emergence was produced by 

 sifting the soil, were tested. In the first experiment hibernating beetles (Tucson 

 A, g. II) were encouraged to emerge by applying water on June 1, when they 

 were removed to the constant-temperature room ; their reactions were found to 

 be positive to light, but negative to gravity. The light response was further 

 tested by placing 5 beetles in each of 10 test-tubes and each tube was placed so 

 that one-half of it was in the shade of the laboratory roof and the other half 

 in direct sunlight. The beetles all oriented and moved out into the sunlight 

 at the end of each tube, where they remained, and in a few minutes were dead. 

 The air-temperature in the exposed ends of the tubes was 57° C. In this experi- 

 ment the organisms reacted to sunlight and the suggestion that possibly the red 

 or blue rays might have influenced this result led to the next test. 



Of 50 hibernating individuals (Tucson A, g. II) emerged after adding water 

 on June 3, 25 were put in each of two test-tubes ; one of which was placed in 

 direct sunlight under a red bell-jar containing a potassium-bichromate solution, 

 and, while no deaths occurred, no definite reaction was observed ; the other was 

 placed in the direct sunlight beside the former, under a blue bell-jar provided 

 with a solution of copper sulphate, when all became positive to the rays and 



