Spheksophobia.

A fear -- or at the least -- a respect for wasps is quite natural.  Laudatory even. Spheksophobia, of course, refers to an unnatural or abnormal fear of the family Vespidae (wasps, hornets, etc. but not including bees or ants).  The truth, however, is that wasps are generally non-aggressive (unlike hornets which are very aggressive) and many varieties (such as ground wasps) are virtually pacifists.

The nest below was built by a colony of paper wasps (Dolichovespula arenaria), anchored on a low branch about eight foot above the ground.  For the entire summer and early fall, we coexisted in close proximity (10-20 feet) without conflict.  Then, come fall, when the nest was abandoned, I harvested it and placed it in a nearby, safe, dry location to see if it would be visited again.  It was not and, next spring, a new nest was constructed several hundred feet away from the original.

Ground view (approx: 6" diameter)

It took me a while to decide how -- I knew from the time I discovered it what I would use it for -- to use this nest as a geocache.  Finally, I took a can of foam insulation and inserted the straw through the entrance (bottom of the nest), probing for a location fairly deep inside, then triggered several shots of foam, judging by feel how much of the nest was being saturated.  The result is not perfectly solid, the outer shell is somewhat soft and flexible but I have a pretty solid core of foam inside, certainly enough to anchor a microcache in a cavity.  (The small, white dot of foam at the entry point has since been rendered black.)

To help preserve the nest, it's been sprayed with several coats of a polyurethane varnish (matt finish) and allowed to dry hanging.  The overall result is that the nest is much darker, changing from a papery gray to a medium brown, but I doubt that the difference in coloration will be apparent to the average seeker.

As seen from above with microcache in center

From the top, I cut a circular opening 1.25" in diameter, then used a speedbit (same size) to bore down for a two inch depth.  The excised portion of the outer skin has been glued to the cap of the already camouflaged container so that, once inserted, the addition becomes virtually invisible except on close inspection.   The results, as you can see, are a very neatly concealed microcache ... and one which should provide a real challenge to the seeker once the assembly is, again, hanging from a tree branch just overhead.

I can hardly wait to see what kind of comments this one brings.  A few screams of outrage perhaps?  Followed by peals of self-depreciating laughter?  But one can only wait and hope.