3io 
Psyche 
[December 
followed at trail’s end: that of a compact mass of ants digging in 
around pebbles, leaves, and grass. When no nest was found, the 
group began moving in widening circles, out as much as 3 feet. After 
2 to 7 minutes of futile search some ants turned homeward, while 
others dug for another io to 20 minutes before giving up. Some of 
the wrong spots seemed quite evidently places where ants had been 
living. One had a pile of excavated soil before a wide open entrance 
into which the ants plunged. Once a colony which had been raided 
3 times previously erected such a good barricade that the Polyergus 
never did get in, although they did not give up for 22 minutes. 
(Later I dug the nest and found the colony still there.) During 
the 2 years n failures occurred in 63 observed raids. Thus, 17.6% 
of the raids ended in failures which seemed to be due to misinforma- 
tion. One ended in disaster because the terrain was too severe. The 
ants started up an almost perpendicular bare bank, but many lost 
their footing and could not get to the top. The whole group became 
disorganized, and eventually all returned home without going any 
farther. 
SPEED OF TRAVEL AND TIME REQUIRED FOR A RAID 
The time of an entire raid was considered as the interval between 
the starting out of a raiding column and the return of the last ant. 
This varied greatly, depending on distance traveled, time required to 
get into a nest, amount of brood to be brought out, and the length 
of time that some ants delayed at the nest before starting home. For 
51 raids the mean time was approximately an hour (63 minutes). 
The extremes were 20 minutes for a raid on a colony 1 5 feet away, to 
2 hours and 19 minutes for one on the most distant colony 286 feet 
away. June raids took a shorter time, averaging 47 minutes in con- 
trast to 73 minutes for both July and August and indicating again 
that near colonies were raided first. 
The preraid organizing, when many ants were moving about on 
the nest, took from 2 to 25 minutes and averaged 9.6 minutes. The 
time taken to reach a raided nest averaged 23 minutes and varied from 
5 to 65 minutes. The opening of a nest, its penetration, and the 
emergence of the first ants with loot averaged 4.4 minutes. If the 
entrance was not obstructed, they could enter immediately; if it was 
barricaded or guarded, they might require as much as 13 minutes to 
free it. Once the ants entered, they would have the first brood out 
within a, minute or two. The journey back took a shorter time than 
the outward one had required. The mean time required for the first 
ant to reach home was 15.9 minutes with a variation of 3 to 47 min- 
