312 
Psyche 
[December 
Brood collected in 19 raids in 1964 averaged 120 (98 pupae and 
22 larvae) a raid. If an estimated 40 successful raids took place 
during the season, the Polyergus captured approximately 4,800 young 
ants (3,920 pupae and 880 larvae). Since there were probably not 
more than one-and-a-half times that number of adult Formica in the 
mixed colony, and since many workers live for a number of years, 
it would seem that a fair proportion of the brood brought in is used 
for food. The success of the 1965 season was similar. Twenty-eight 
raids brought in a mean of 116 young ants consisting of a mean of 
90 pupae and 26 larvae. 
Ants counted as they reached the home nest fell into three cate*- 
gories: those with pupae, those with larvae, and those with nothing. 
The proportion varied greatly from an extreme of a successful raid 
in which 438 carried brood and only 18 did not, to an unsuccessful 
one in which 32 carried brood and 410 returned without. In 1964, 
48% of the ants returned wihout brood, while in 1965 the unsuccess- 
ful ones constituted 66%. The second season may have been simply 
a bad year; or perhaps after a Polyergus colony reaches a certain 
size, the number of brood captured depends not on the strength of 
the raiding force but upon the number of F. p. nitidiventris larvae 
and pupae available. 
An unusual method of collecting brood was seen in 1967 when a 
Polyergus colony raided another Polyergus-Formica p. nitidiventris 
colony at least twice. On the raid seen on August 15, the timing 
was perfect. Ants from nest “a” traveled for 28 minutes to nest “b,” 
reaching it 8 minutes after all of its Polyergus had started on a raid. 
There was no barricade, and no fighting, and the 76 ants from nest 
“a” made off with 68 pupae and two larvae. The last ant, carrying 
a pupa, left just as the nest “b” Polyergus returned. They had also 
made a successful raid, in which 98 ants returned with 97 pupae 
(and many ants started off immediately over the same trail to bring 
in more pupae). 
Nest “a” had been discovered in 1966, and it seems possible that 
it is the old Lawn Colony which remained in one place from 1956 to 
1965. If this is true, it had moved 61 feet late in 1965 or early in 
1966. 
RELATIONSHIP WITH OTHER ANTS 
The 0-26 colony raided only F. p. nitidiventris. The Lawn Colony 
raided F. p. nitidiventris , F. lasioides Emery, and F. neogagates 
Emery; but only the first species were seen at the home nest. 
