194 ' E. A. ANDREWS 



as high, but from this size they run up to 50 mm. The largest 

 may have several distinct passageways inside and seem to arise 

 from union of smaller arcades which each contain but one cavity. 



Through these arcades the termites run rapidly to and from 

 the nest in small bands or flocks of less than a dozen which 

 may, however, often fuse with those before and behind to make 

 continuous lines. The termites do not stay on the right or the 

 left but sometimes cross, thus creating unnecessary friction with 

 files coming in the opposite direction. When the number run- 

 ning becomes great enough the individuals run two or more 

 abreast and while usually on the floor the larger numbers may 

 crowd the arcade till many run upon the ceiling as well and 

 the arcade is full of the flowing multitudes always going in 

 opposite directions, unless under some unusual stimulus of 

 fright when they may pour along in one direction and soon 

 leave the arcade empty. 



The rate of locomotion was found to be about 15 mm. per 

 second, or three lengths per second. 



The way the termites construct the walls of the arcades was 

 seen when old arcades were broken and restored, when new 

 ones were made from nests transported to new trees and from 

 experimental nests kept in aquaria or hung from the ceiling. 



In constructing a new arcade there is first established a definite 

 path along which the termites run for hours or days to and fro ; 

 then the sides of this path are gradually walled in, and finally 

 a roof built over all. The first walls are laid down in sections 

 of a few millimeters length at irregular intervals and irregularly 

 right and left. These pieces are gradually connected and arched 

 over: the part of the arcade nearest the supply of building 

 material is completed first. Within ten days a much disturbed 

 and decimated colony transported to a new tree built some nine- 

 teen feet of arcade. In normal communities a foot of destroyed 

 arcade is replaced in a night. When the side walls are but 2 to 

 3 mm. high they are already arched inward over the track to 

 form the beginning of the arched roof of the arcade. 



The walls of the arcade are about | of a mm. thick and externally 

 covered with fragments from i to i mm. in size stuck together 

 by some dark material. Internally the walls are smoother and 

 made more largely of the dark cement. Observing the termites 

 we see that workers turn aside now and then to form the walls : 



