INTEGRATION OF AGGREGATIONS 93 



the organization of ant colonies. But on this point there are other 

 observations to the contrary (Fielde and Parker, 1905). 



Beebe (1916) thinks that there is a close correlation between habi- 

 tat and habits of tropical birds and the development of their voices, 

 which are popularly supposed to be one of the most striking attri- 

 butes of tropical birds. He reports that sohtary birds, living in the 

 open country where the view is more or less uninterrupted, have a 

 tendency to possess negligible voices. Inhabitants of dense jungle, 

 if relatively solitary, have remarkable vocal powers, with loud 

 staccato calls or with insistent rhythm, by means of which they com- 

 municate with their unseen fellows. Such birds may be nocturnal in 

 habit. Birds living in pairs or in families have, for the most part, 

 vocal organs which they use to good effect; but they lack the super- 

 lative voice development of solitary birds. Birds living in flocks have 

 voices that are still less in evidence, though there are notable excep- 

 tions to this rule, as, for example, the parakeets. 



In the matter of vocal performance, as with tactile and visual 

 integrations, group unisons have been reported. The group singing 

 of the western meadowlark is an example among birds. One of the 

 most interesting cases is that of the snowy tree cricket, which has 

 been much studied and which Fulton (1925) reported to effect 

 changes of chirping rate in order to chirp in unison. 



ShuU (1907), a careful and critical observer, concluded early in 

 his studies that real synchrony does exist in the chirping of the tree 

 cricket; but later he somewhat modified this opinion, saying that 

 while he still believed that the singing insects do influence one an- 

 other, he believed that cases of exact synchronism were usually 

 accidental. Lutz (1924) was skeptical both concerning the fact of 

 synchronism and concerning its importance with tree crickets. Ful- 

 ton (1928, 1928a) in recent studies appears to have furnished con- 

 clusive evidence that the Oecanthus song is both rhythmical and 

 synchronous. After the usual listening tests, revealing almost per- 

 fect synchronism, a number of the singing insects were placed in 

 another cage at some distance, and the front tibiae containing the 

 auditory organs were removed. This effectively broke up the syn- 

 chrony except at those times when the individual rhythms appeared 



