64 WALTER N. HESS. 



dome and regurgitates the moist earth in the form of a short 

 ribbon-like mass, which it applies to the walls of the chamber. 

 By the frequent repetition of this process, the lattice-like frame- 

 work finally entirely covers the larva (Fig. 14). Even after it 

 forms a complete dome, the larva can be seen for several hours 

 between the meshes, before it is entirely concealed. By re- 

 peatedly removing the earth from the bottom of the chamber 



FIG. 14. Pholurus pennsylvanica pupal chamber completed, lateral view. 



and adding it to the inside of the dome-like wall, the chamber 

 is deepened, and its covering is strengthened and made thicker. 



The completed chamber is in the form of an elliptical depres- 

 sion in the ground, about one half of an inch in length and about 

 seven sixteenths of an inch in width. Even after the larva con- 

 ceals itself it continues to add to the walls of the cell until they 

 are from one eighth of an inch, to as much as one half of an inch 

 in thickness. 



The time spent in building the pupal-cell is about two days, 

 though larvae sometimes continue to excavate for three or even 

 four days, making a firmer and thicker covering for their cells. 



That the intestinal secretions of the larva are used for moist- 

 ening the earth, which is used in constructing the cell, there can 

 be little doubt, yet it evidently has no special adhesive content, 

 for the pupal-cells are easily broken, and they seem to offer no 

 more resistance than ordinary earth which has dried, after 

 having been mixed with water. This liquid seems to serve simply 

 as a fluid in which to mix the earth and make it plastic. 



From the examination of several of these completed pupal- 

 cells, it seems evident that the method of construction is such as 

 to allow a small amount of air for respiration to pass in and out 

 between their meshes. Some of the domes of the completed 



