Sept. 1899] Lander: On the Seventeen-Year Cicada. 213 



of their singular mud structures capping their burrows ; one of them 

 fairly well preserved as to shape, but badly washed. Probably a more 

 extended search would have revealed others, though few could have 

 stood the long rains. 



Early in April, 1894, I discovered several widely extended areas 

 thickly studded with sun-baked mud Cicada huts, three or four inches 

 high, built in extension of the burrows at the surface of the ground ; 

 the first account of which was published in the New York Times. 

 Subsequently I offered in the Scientific American a theory as to the 

 cause of the phenomenon and a more extended notice in this journal 

 for March, 1895. 



I had observed that the huts were weather-worn as if from rain. It 

 was evident that they had been built in March, which I remembered 

 was an unusually warm month. Inquiries at the weather station in 

 New York showed that that month had been the hottest March of 

 which there was any record. 



It seemed probable that the builders of the huts had been prema- 

 turely stirred to activity by the phenomenal warmth, but the colder 

 weather that followed prompted them to close their burrows with mud 

 caps to await a more propitious season or full maturity to cast their 

 pupa-cases and emerge in their imago state. 



Of course there was some special reason for the close aggregation 

 of such vast numbers of huts in more or less well-defined limits. 

 Investigation showed that in all the hut areas I discovered the soil was 

 thinly overlying a rocky foundation, either near quarries or on top ot 

 the rocky hills, and on the Palisades, worn down by glacial action. 

 Some areas had been recently burned over, exposing the soil to the full 

 heat of the sun. 



It seemed probable, therefore, that the abnormal heat of March 

 and the fact that the hut-builders were in shallow burrows were the 

 causes that had impelled the insects to prematurely open their burrows 

 which they subsequently closed with mud caps, Of course any pupa 

 that happened to be near the surface, no matter how deep the soil be- 

 neath it, would be like affected. 



This brief summary is for the purpose of accentuating the fact that 

 the finding of Cicada huts in 1898 under exactly the same circum- 

 stances goes far towards demonstrating the truth of the theory. 



March of 1898 was very warm ; the weather bureau at New York 

 reports that the mean temperature was but |- of one degree lower than 



