136 
Psyche 
[December 
porary seasonal affair like the nest of a wasp but may be of very 
considerable permanence, one of the most enduring architectural 
results of insect communism. In considering possible reasons 
for differential success and failure as between mounds near to- 
gether, it must be born in mind that these ants are long-lived 
amongst insects. Ants were kept in captivity by Lubbock for 
five or six years as workers and up to fifteen years of age in the 
case of a female ant. 
In nature ants of this species lie dormant about four months 
of the year and it may be that thus they live longer than in cap- 
tivity; nevertheless it is probable that the mound may outlast 
the lives of the original builders and be possessed throughout 
the generations. 
Some of the mounds mapped in 1905 were already large and 
remained active in 1920 and even in 1926. To attain that large 
size probably requires several dr many years judging from the 
measurements elsewhere recorded (Andrews, Growth of Ant 
Mounds, Psyche, 32, 1925); so that a mound already large in 
1905 may at this present writing be over thirty years old which 
is in harmony with the estimates of McCook as to the time that 
one mound may endure and in agreement with the fact that Forel 
had a prosperous mound of a related European ant under obser- 
vation for forty years. The final end of the existence of a mound 
may be like that of a human city, variable, complex and to be 
known only by detailed history — which has not as yet been 
written up to the last day of any ant mound. 
That the mound may persist longer than the original found- 
ers of the mound is probable also from a described habit of this 
ant to seize upon young female ants after swarming and to get 
them into the old mound in some cases so that many mothers of 
different ages are actually found in a well advanced mound. 
Hence the deficit of population from old age may be compensated 
for and the tribe or family be able to live on in the same old 
mound, if all goes well. 
As to empty mounds: beside desertion by migration any 
one mound may lose its inhabitants either from internal or ex- 
ternal causes, (sufficient disease or epidemics are not yet known) 
but old age of the inhabitants would lead to an empty mound if 
