PSYCHE 
Vol. 76 
December, 1969 
No. 4 
A UNIQUE PREDATORY ASSOCIATION 
BETWEEN CARABID BEETLES OF 
THE GENUS HELL U O MORPH OIDES AND COLONIES 
OF THE ARMY ANT NEIV AMYRMEX NIGRESCENS * 
By Howard R. Topoff 
American Museum of Natural History, New York, N.Y. 10024 
This paper presents preliminary observations of a unique relation- 
ship between predatory beetles, H elluomorphoides latitcirsis LeConte 
and H. ferrugineus Casey, belonging to the family Carabidae, and 
colonies of the army ant, N eivamyrmex nigrescens (Cresson). 
Studies of interactions between these beetles and N. nigrescens 
are important because : ( 1 ) they have revealed unique predatory 
interactions between species of Helluo?norphoides and colonies of N. 
nigrescens ; and (2) they have increased our understanding of the 
role of the kinds of stimulation involved in group raiding and emigra- 
tions in army ants. 
In southeastern Arizona, colonies of N . nigrescens are characterized 
by large populations, group predation, and cyclic behaviour consisting 
of alternating nomadic and statary phases (Schneirla, 1958). Col- 
onies contain 150,000 to 250,000 workers and a brood population of 
approximately 30,000 individuals. In the study area, during the 
nomadic phase, raiding begins at dusk and is followed by emigrations 
to new nest sites. These predatory forays and emigrations are con- 
ducted on branching anastomosing chemical trails, laid down con- 
tinously from the hindguts of the ants (Watkins, 1964). Worker 
ants maintain their positions in the columns by following these trails, 
and by close contact with adjacent individuals. 
*This study was supported by NSF grant GB-7602, and conducted at the 
American Museum of Natural History’s Southwestern Research Station. I 
thank Miss Beverly Greenspan for her assistance as a participant in the 
NSF Undergraduate Research Program. I also thank Dr. George Ball for 
identifying the species of H elluomorphoides. 
Manuscript received by the editor December 11, 1969 
375 
