34 
Psyche 
[September 
spread form of communication in ants. Perhaps further directed ob- 
servation will show it to be more common than the meager existing 
data have indicated. 
It is valuable to speculate, as Hingston (1928) and later Sudd 
(1959) have done, that tandem running is a primitive communication 
form that can lead in evolution to trail laying. Hingston has des- 
cribed what appear to be excellent intermediate stages between tan- 
dem running and trail laying in the Indian species Camponotus (Myr- 
mosericus) paria Emery and C. (Tanaemyrmex) compressus (Fabr. ). 
In paria the leader ant does not halt and wait to be touched, while 
the follower often drops behind 2 or 3 inches and seems to be orienting 
at least in part by a rudimentary odor trail. The behavior of compres- 
sus resembles that of paria except that as many as ten or twenty work- 
ers follow in a single file behind the leader. 
Nevertheless, it will have to be remembered that in Cardiocondyla, 
at least, tandem running is a highly evolved behavioral pattern in its 
own right. It can be fairly said to include more complex individual 
behavior than trail-laying and trail-following. In particular, the 
simultaneous release of a chemical stimulus and the drive behavior of 
the leader ant are quite elaborate in comparison with other known 
forms of ant communication. Even so, it would be most interesting 
to know whether any of the other species of Cardiocondyla show be- 
havior patterns intermediate between tandem leading and trail-laying, 
as is apparently the case in Camponotus. 
Literature Cited 
Hingston, R. W. G. 1928. Problems of instinct and intelligence. Arnold. 
Sudd, J. H. 1959. Interaction between ants on a scent trail. Nature, 183 : 1588. 
Wheeler, W. M. 1908. The ants of Puerto Rico and the Virgin Islands. 
Bull. Amer. Mus. Nat. Hist., 24: 117-158. 
