277 



which are built by the pupa of the periodical cicada above ground 

 shortly before the adults issue. Dr. Lintner brought together the facts 

 concerning a large number of observations made the present year, and 

 showed that the earlier supposition of Eiley and others, that these 

 chimneys are built only in wet ground, is unjustilied, and showed fur- 

 ther that the orifice at the bottom of the chimneys and next to the sur- 

 face of the ground, as figured by Riley, is at least abnormal. Dr. Lint- 

 ner was, however, unable to give a satisfactory explanation of the cause 

 of this chimney-building. 



Mr. Benjamin Lander, in the Scientific American for October 13, pub- 

 lishes a lengthy communication on the same subject, accompanying it 

 with very good illustrations of the chimneys, both entire and in section, 

 and offering an explanation which is new. His observations lead him 

 to believe that these chimneys are built only where the soil is very thin 

 and covers a rock ledge. He showed further that the month of April 

 was phenomenally hot, and he concludes that the puppe in the shallow 

 earth, covering the smooth, unbroken, impervious rock, would be early 

 stirred to activity by the unwonted heat, and would build their burrows 

 to the surface in advance of those in deejier and cooler ground, obeying 

 the same impulse that the latter would feel when the warmth of the 

 more advanced season should reach their more remote abiding places. 

 Especially would this be the case where the woods had been recently 

 burned over, as was the case with several chimney localities which Mr. 

 Lander observed. The closed extensions to the short burrows Mr. Lan- 

 der therefore supposes to be built as a i)rotection from premature heat 

 and possibly to shut out injurious intruders during the accidentally 

 lengthened period which they would have to wait for ftill development. 



This strikes us as an ingenious theory, and likely to be to a certaiu 

 extent correct, provided no exceptions to the rule of shallow soil be 

 found. Our own experience with these chimneys is, however, too 

 limited to justify criticism. A well-known entomologist recently sug- 

 gested to us in conversation the idea that inasmuch as the chimneys 

 are most frequently built upon ground which is comparatively free 

 from trees and shrubs, they are constructed to provide the pupa with 

 an eminence upon which to crawl and to which to attach itself while 

 shedding its skin and unfolding its wings. That it seems necessary 

 for the insect to crawl upon a tree, a shrub, a fence, or something of 

 that sort to perform this operation is well known, and this theory, too, 

 is therefore very plausible, provided it be found that the chimneys are 

 confined to comparatively open places. If we remember correctly, 

 however, one of Dr. Lintner's photographs showed the chimneys to be 

 very abundant in a patch of comparatively dense undergrowth, and we 

 have also seen them in a grove of large trees. 

 8359— No 3 5 



