1958 
Wilson — Ant Species in New Guinea 
29 
leaf litter as in open aspect; underlying leaf mold rich and 
moist; soil loose, well aerated and drained and relatively 
moist; moss common on the surface of the ground, on 
rotting wood lying on the ground and on tree trunks; 
A-stratum trees average 40 meters or more in height ; plank 
buttresses common; lianes and epiphytes abundant; under 
growth sparse, making human progress across the forest 
floor easy. The majority of endemic ant species are con- 
centrated in this division. Examples of genera that reached 
maximum density (in 1955) on the floor of the Busu forest 
included Ponera, Myopias , Ectomomyrmex, Pheidole, Stru- 
migenys , Rhopalothrix, Myrmecina, and Pristomyrmex. In 
the canopy Iridomyrmex heavily predominated. 
“Dense rain forest”. Closed canopy; little or no ground 
insolation ; leaf litter thin, with one-quarter or more of the 
ground surface completely bare; leaf mold very poorly de- 
veloped; soil dense, less well drained and moister than in 
medium forest; parts of the ground surface occasionally 
holding shallow pools of water after heavy rains; moss 
abundant, especially on larger rotting logs ; A-stratum trees 
as tall as in medium forest; plank buttresses common; 
lianes and epiphytes abundant; undergrowth very sparse, 
even more so than in medium forest. Ants reaching max- 
imum density in various strata of this division at the Busu 
River included some species of Pheidologeton , T etramorium, 
Leptomyrmex and Iridomyrmex. 
Careful analysis would probably reveal many finer details 
of microgeographic segregation than those indicated here, 
for the rain forest is an extraordinarily complex mosaic of 
local habitats, exhibiting seemingly endless nuances and 
combinations of erosion states, growth and death of vegeta- 
tion, composition of leaf mold, and other environmental fea- 
tures. Ant species did not appear to be limited to any of 
these particular divisions within the rain forest proper. At 
most, the divisions probably serve as density foci, from 
which the species are constantly pressing out into adjacent, 
less favorable habitats, 
Geographic patchiness. Ant species apparently show exten- 
sive and unpredictable variation in population density over 
short geographic distances above and beyond that already 
