1974 ] 
Brown — Ant Genus Proceratium 
79 
spread extinction of stictum- group stocks ensued ; although it is not 
easy to visualize significant competition among such rarely-collected 
species, I should point out that the adaptive zone (predation of spider 
eggs) is a limited one. Furthermore, advanced methods of collecting, 
at least in North America, have proven that some advanced Procera- 
tium species are common in suitable microhabitats. These micro- 
habitats are, so far as we can tell, all cryptic ones — above all, in 
large masses of well-rotted wood. This may, of course, be an artifact 
of biased collecting methods, but I doubt it. On the northern fringes 
of the range of Proceratium — for example, in the environs of Bos- 
ton — P. silaceum and P. pergandei are taken occasionally, but always 
under rocks in the soil. Farther south in the U.S., almost all 
collections are made deep in rotten wood or in humus and litter near 
rotten wood. The type series of P. goliath came from a rotten log 
in wet tropical forest. 
The microhabitat of P. avium , to judge from the limited observa- 
tions I have made, differs strikingly from that of other Proceratium. 
Certainly, the nest site is different. The first nest of P. avium taken 
on Mauritius came, it is true, from a hollow rotting stick lying on 
the forest floor. This may be a common kind of site for the species, 
yet very many such branchlets were examined on the day of collection 
without success, and it is possible that the branchlet had fallen re- 
cently from a tree above. In any case, I have never seen any of the 
eight other Proceratium species collected alive by myself in various 
countries nesting in such a large cavity in such an exposed site as was 
the colony in this stick. The other two P. avium nests seen were of 
course arboreal, with the foraging trails openly exposed for some 
meters over open soil and tree trunk. The ground and arboreal nest- 
ing sites for ants in wet tropical montane forest are rather academi- 
cally distinguished in any case, but it seems to me that the exposure 
of the nests and foraging trails of P. avium is what is significant here. 
If other species of Proceratium forage so openly day or night, it has 
not been noted as far as I know, and indications are against it. 
Of greatest interest is the contrast in habitus, especially that part 
owing to sculpture and pilosity, between P. avium and its congeners. 
In P. avium , the looser, coarser, more shining integument and its 
fairly long open pilosity may be compared with the finely rugulose- 
punctate or reticulopunctulate sculpture and very short, fine, more or 
less dense pilosity of the other Proceratium species. There is every 
reason to believe that these fine, crowded punctures and their associ- 
ated hairs are a specialized evolutionary development (pushed further 
