THE EMIGRATION BEHAVIOR OF TWO SPECIES OF 
THE GENUS PHE1DOLE (FORMICIDAE: MYRMICINAE). 
By Robert droual 1 and Howard Topoff 2 
Introduction 
Colony emigrations are common among ants (Wilson 1971) and 
occur for a diversity of reasons. However, except for the legionary 
ants, in which colony emigrations are an inherent part of the 
foraging ecology (Wilson 1971), and species which inhabit delicate 
and easily disturbed nests (Holldobler and Wilson 1977, Moglich 
1979), emigrations are thought to occur infrequently. Here we 
present evidence that two species of the genus Pheidole, P. deser- 
torum Wheeler and P. hyatti Emery, emigrate frequently under 
environmentally stable conditions. We further advance the hy- 
pothesis that the surplus nests resulting from these emigrations, 
reduce the secondary losses which occur as a consequence of the 
panic-alarm defense these species employ against army ants of the 
genus Neivamyrmex, by serving as temporary shelters and centers 
for colony reorganization. 
Methods 
This investigation was conducted during the months of June, July 
and August, 1980, at two different study sites. One site was an oak- 
juniper woodland located on the grounds of the Southwestern 
Research Station of the American Museum of Natural History near 
Portal, Arizona (elev. 1646 m). The other site was a desert-grassland 
located 8 km N.W. of Rodeo, Hidalgo Co., New Mexico (elev. 1250 
m). In both habitats a winter (Dec., Jan., Feb. and March) and a 
summer (July, June and August) rainy season occur. On the oak- 
juniper woodland site colonies of both P. desertorum and P. hyatti 
were located and marked; on the desert-grassland site only colonies 
of P. desertorum were located and marked. 
'Biology Program, City College of C.U.N.Y., New York, N.Y. 10031 
Psychology Department, Hunter College of C.U.N.Y., New York, N.Y. 10021 and 
Department of Entomology, The American Museum of Natural History, New York, 
N.Y. 10024 
Manuscript received by the editor June 8, 1981 
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