The Potato Beetle in a Deseet 353 



breed and produce a hibernating winter generation, may be buried after having 

 been induced to enter the ground through desiccation; furthermore, that the 

 animals lived many months when buried under these conditions, but that the 

 death-rate was greater in the sand, and the majority in the open plot succumbed. 

 These data are also given in Table 4. 



On the other hand, the second set of experiments concerned beetles of the 

 winter generation which had just emerged from the pupa state. This problem 

 was considered from three aspects : (1) Some animals were buried with all their 

 activities normal; (2) others were induced to hibernate through partial desicca- 

 tion produced through adverse conditions, and were then buried; (3) many 

 were allowed to hibernate normally before they were finally buried in the two 

 plots. 



For the first test in which the animals were buried with all their activities 

 normal, 400 emerging adults (Tucson A, g. II) were collected on September 10 ; 

 they were placed within the sand and adobe portions of the two plots. During 

 the winter, and until May 1, they were left unmolested, when tubes from each 

 plot were examined and no living individuals were discovered. On October 1 

 the remaining tubes were exhumed, but no live animals were found. These 

 results showed that, when beetles of the winter generation, which normally 

 hibernate, were buried with all their activities normal, hibernation was unsuc- 

 cessful and all the animals succumbed (Table 4). 



In the second test, where beetles were induced to hibernate through desicca- 

 tion, 1,000 emerging adults (Tucson A, g. II) were collected on September 11, 

 and were placed under adverse conditions in pedigree cages in the vivarium, 

 where their food was sliced potato, as in a previous test. On October 2, hiber- 

 nating adults to the number of 692 were sifted from the soil, and 308 dead ones 

 were gathered from its surface ; 400 of the living insects were then divided into 

 8 groups, and were buried within the soils of the two plots, in order to afford 

 the opportunity of winter hibernation. On May 1 these tubes were examined 

 for living beetles ; the tube from sand under the covered plot contained no living 

 adults, while in the one from adobe earth were found 48 living adults ; also those 

 in sand from the open plot contained only 26 living individuals, while 45 beetles 

 were removed from the tubes in adobe. In a similar manner, on October 1, the 

 remaining 4 tubes were removed. In the adobe soil tube, under the shelter, 

 were found 39 animals, but no individuals hibernated successfully in sand; 

 moreover, tubes from the open plot harbored no life. The results indicate that 

 induced hibernation was effected in the winter generation through desiccation, 

 which increased the resistance of these animals by decreasing their normal 

 activities. The only insects alive at the end of the experiment were found in 

 adobe under the covered plot, which proved that potato beetles, when hiber- 

 nating in adobe, possessed a greater resistance to desiccation than when buried 

 in sand (Table 4) . 



In the last test, insects were permitted to hibernate normally, then buried in 

 Plots A and B. This was a control for former tests, since it showed that no 

 error was introduced through handling or digging up the animals. For this 

 test, 1,000 emerging adults (Tucson A, g. II) were collected on September 13; 

 they were placed in a large out-of-door cage that was provided with potato 

 plants, and other environmental conditions were apparently normal. After 

 consuming much food, these animals were in hibernation by October 7 ; then, 

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