546 



THE AMERICAN NATURALIST 



[Vol. LIV 



on May 18, the first adult was seen making its weak flight over 

 my garden, having emerged some time during the previous night. 

 A few evenings later the great exodus had begun in earnest and 

 thousands of pupa? were issuing from the ground after sundown 

 and ascending all the bushes, trees and posts in the vicinity to 

 transform. 



Although the actual exodus from the ground does not take 

 place until after sundown each evening, the pupae, in preparation 

 for the event, excavate their burrows to the very surface of the 

 ground and await the setting of the sun. In some instances the 

 creatures burrow just to the surface, leaving a very thin layer 

 of soil undisturbed over the exit. Frequently a tiny hole is punc- 

 tured in the center of this thin surface layer. If these burrows 

 are cautiously approached late in the afternoon long before sun- 

 down, the heads of the creatures may be seen near the surface. 

 As the light intensity wanes with the oncoming of evening, the 

 creatures come to the very surface, but quickly retreat if ap- 

 proached or disturbed. It is evident that the pupae are nega- 

 tively phototropic. If a pail or box is inverted over their bur- 

 rows long before sundown so as to exclude the light, the creatures 

 will shortly emerge as if night were really at hand. In this way 

 I have brought many pupae out of their burrows in broad day- 

 light. 



Although the pupae quickly transform after emerging from the 

 ground, it would be of interest to know just what conditions, ex- 

 ternal or internal, determine the impulse to prepare for the adult 

 stage. If the creatures are prevented from leaving the ground 

 or soil, the following experiments indicate that the pupae will 

 remain as such at least a day or two longer than when allowed to 

 ascend trees and shrubs in the normal manner. 



On the evening of May 24, five pupae just emerging from the 

 ground were captured and placed on the damp bare ground be- 

 neath a large inverted flowerpot, the drainage hole at the bottom 

 of which had been closed. In addition to these, six other pupae 

 were captured and placed in a large flowerpot of similar size 

 filled even to the top with loose soil. This pot was covered with a 

 board. Both pots were examined next morning. The pupa} 

 placed on the bare ground beneath the inverted, empty flowerpot 

 were still crawling around, and none had transformed. Of the 

 six placed in the pot containing soil, one had died. The remain- 

 ing five were alive and active, and likewise none of these had 

 transformed. 



