282 Fiftieth Keport ox the State Museum 



interesting observations of Mr. Lawton on the repairing of injured cham- 

 bers. He found that in every case, except one, the pupte repaired 

 them soon after the injury by brir.ging up pellets of mud and roof- 

 ing over the broken portion about half an inch from the top. The 

 repairs were begun on one side and gradually extended over the open- 

 ing horizontally, there being no attempt to form a dome-shaped roof. 

 Some of the chambers which had been broken off at 12 : 15 P. M., were 

 found with a few pellets in position at 12 145, and three hours later the 

 opening was entirely closed over. At one time a pupa was caught with 

 a pellet of mud in its claws. 



When the time for the linal transformation has come, the pupa 

 makes its way out of the chamber through a rounded hole made by it 

 near the top, of a size barely sufficient to admit its passage. 



The Purpose of the Chambers, 



Most of the habits of animals are of direct advantage to them, or else 

 they may be explained as the persistence of some formerly useful, but 

 which under changed conditions are no longer of value. The Cicada 

 buildings were first found on low wet soil after heavy rains, and the 

 natural inference was that they were constructed for the purpose of escap- 

 ing excessive moisture or flooding. In 1894, they were first noticed on 

 tracts recently burned over, or in places where the soil was comparatively 

 shallow. The early spring had been unusually warm, and the theory was 

 advanced that these structures were reared to protect the insects from the 

 heat — the elevation and slope of the land in many cases rendering the 

 earlier theory untenable. Unfortunately for this explanation, the pupse 

 persisted in building their above-ground chambers where the soil was far 

 from shallow — under the leaves in woods not recently burned over, 

 and in other places where the ground would not become unnaturally 

 heated. It should also be remembered that the pupse had only to 

 descend to a m.oderate depth if uncomfortably warm, and that in open 

 fields, at least, the above-ground chambers would be much warmer on 

 a sunny day than a subterranean burrow. Moreover, their occurrence, 

 sometimes almost covering large tracts, and again alternating with open 

 burrows or disappearing altogether, renders a broad generalization con- 

 cerning their purpose extremely unsafe. 



It may be, as suggested by Mr. Lander, that the above-ground cham- 

 bers are the work of those coming to the surface earlier than the proper 

 time for their final change, as they were probably built in April or early in 

 May, while the imago did not appear as a rule until the latter part of 



