1986] Heere, Windsor, and Foster — Wasps and ants 327 
The perceived avoidance was substantiated when we moved a 
twig that the Eciton ants were using as a bridge against a stem of M. 
poeppigii. The army ants stopped when they came in contact with 
the stem and although ants from the rear continued moving forward 
until there was a great tangled mass of ants at the front, no ants 
crawled onto the stem. Next, we placed stems of Tococa guianensis 
and Maieta poeppigii with intact leaves and formicaria across active 
Eciton trails and found that the trails were quickly rerouted around 
the plants. Similar responses were not obtained when we placed 
other plant species or Tococa guianensis without Allomerus inhab- 
itants across the path of the army ants. Further, in three instances, 
we observed army ants passing by T. guianensis plants with Allome- 
rus ants and active wasps nests. We removed two T. guianensis 
leaves minus formicaria with attached wasp nests, placed them on 
twigs at the same height off the ground as they had been on the 
plants, and put the twigs in front of the Eciton raiding swarms. In 
both instances the army ants swiftly scaled the twigs and seized the 
wasp brood. 
Discussion 
Predatory ants pose a particularly important threat to the nests 
and broods of tropical wasps (Jeanne 1972, Litte 1977). In discuss- 
ing this problem in his revision of the genus Mischocyttarus, 
Richards (1945) states, “A number of species have entered into some 
sort of association with ants and have thereby found safety by firmly 
grasping the nettle.” Clearly the wasps nesting on these plants 
benefit by having a neutral border maintained for them. With access 
to the sole connection to the terrestrial world guarded by Allomerus 
or Pheidole ants, there is little or no risk that hostile army ant 
species will come plundering down the pedicel. In this light the unus- 
ual (for Mischocyttarus wasps) nest architecture of M. insolitis 
becomes more comprehensible. 
As Jeanne (1979) demonstrated, building a highly subdivided nest 
composed of multiple combs uses materials for nest construction 
very inefficiently and requires a much higher expenditure of time 
and energy per cell than does the nest architecture more characteris- 
tic of polistine wasps. However, a highly subdivided nest no longer 
provides as concentrated a target for a bird which plunders by 
knocking down whole nests and then leisurely eating the brood (eg. 
