1L'52] 
Creighton — Camponotus papago 
161 
this reaction might be due to a scarcity of trees which have 
twigs with a suitable central pith cavity and this may be 
a part of the explanation. But it now seems certain that 
moisture plays a large part in the choice of nest site. I 
had realized that papago usually nests in limb stubs which 
point upward long before I saw any significance in this 
response. But on one occasion I was examining limb stubs 
immediately after a heavy and prolonged rain storm. I 
found that the stubs which pointed upward caught and 
held the rain water much as a cistern would. Rain soaked 
into the fractured upper end of the stub and accumulated 
at its lower end. The lower end was often so wet that water 
would drip out of it after the stub was knocked loose from 
the tree. In contrast, the horizontal stubs and those which 
pointed downward caught far less rain. The latter were 
often quite dry inside, despite the fact that they had been 
drenched with rain for several hours previously. It thus 
appears that the female of papago , in choosing a nest site 
in limb stubs which point upward, takes advantage of a 
natural system of water conservation. This could certainly 
be one reason why the nesting habits of papago differ from 
those of the eastern twig-dwelling species. It may be added 
that the preference of this ant for nesting in the stubs of 
broken-off limbs seems to be one factor which has kept 
it out of the hands of collectors. It was some time before I 
realized that the most important piece of equipment needed 
to collect C. papago is a heavy axe. The nests are almost 
always built in sound, hard wood and it is not easy to get 
the insects out, even after the stub has been knocked loose. 
The ants which are in the lower passages can often be 
jarred out by whacking the stub with the back of the axe. 
But to get all of them the stub must be split into pencil- 
sized pieces. Anyone who makes a practice of collecting 
papago will never lack for exercise. 
The majors of C. papago, when disturbed, have a curious 
habit of exuding from the mouth a sticky, greyish fluid. 
This often spreads backward over the truncated portion 
of the head. If it is allowed to dry there it forms a crust 
that is almost impossible to remove. As to what the use 
of this fluid may be is hard to say. It may have repellant 
