PSYCHE 
Vol. 66 
September, 1959 
No. 3 
COMMUNICATION BY TANDEM RUNNING IN 
THE ANT GENUS CARDIOCONDYLA 1 
By Edward O. Wilson 
Biological Laboratories, Harvard University 
During field work in Puerto Rico in June, i960, the author had 
the opportunity to study a hitherto little known form of communica- 
tion among worker ants. This behavior, which for convenience might 
be called tandem running, involves the movement outward from the 
nest of closely coupled tandem pairs, and it apparently functions as 
a substitute for trail-laying to recruit fellow workers to food sources. 
On Puerto Rico, tandem running was studied more fully in the species 
Cardiocondyla venustula Wheeler but was also observed in a second 
member of the genus, C. emeryi Forel. 
Natural History of C. venustula on Puerto Rico 
This species has been introduced by modern commerce into the 
West Indies and is probably native to some part of the Old World 
tropics. Wheeler (1908) in 1906 and the present author in i960 
found it abundant in the lowlands of Puerto Rico, especially in urban 
and other cultivated areas near the shore. The following generaliza- 
tions are based on my i960 observations, pertaining mostly to two 
colonies in urban Santurce. 
As also noted by Wheeler, venustula colonies are small, in maturity 
containing probably no more than one or two hundred workers. Nests 
are built in open soil. Both Santurce nests were polydomous, with 
two or three entrances no farther than two meters apart. In each 
case most of the colony was concentrated in one of the subnests. 
Workers were often seen transporting brood and other adult workers 
between the subnests. In adult transport, the two ants face each other, 
and one grips the other by some part of the head (probably the 
mandibles) and swings it over its back; the transported worker as- 
‘Based on research supported by a grant from the National Science Found- 
ation. 
29 
