Testing Cone Sampling Efficiency In California

Yesterday in my post about Columbia Historic State Park I mentioned that I was using my cone sampling time in California to test the efficiency of my cone tapping method.  A friend has asked me to elaborate on that.  I am happy to do so.

When I began tapping cones back in 2008, I devised a sampling method on the spot that I've been using ever since.  It consists of simply whacking the cone against the inner wall of my net while holding the net against my thigh, so as to create a solid striking surface.  (If you try this, note that it helps to have coins or keys in your front pocket so that any prickles on the cone scales don't pierce your skin.)  I hold the cone upside-down and as close to its base as possible, and rotate it a few times in the course of giving it numerous whacks.

How good is this method at dislodging all the spiders from a cone?  That's the question I'm trying to answer with these California samples.  Here's how:  After tapping a cone as described above ("tapping method"), collecting the dislodged spiders and clearing the net, I next used pliers to pull the cone scales from the core and let the scales and any remaining spiders fall into the net ("peeling method").  Before searching the debris for spiders, I gave the remaining cone core a few more whacks into the net.

The number of spiders I collect from cones by the tapping method divided by the sum of the "tap" and "peel" spiders gives me a measure of the efficiency of the tapping method.  In equation form:  Tapping Efficiency = T/(T+P).

The peel method may not be a perfect control, since usually only the cone's small basal scales can be completely pulled free from the core.  Larger scales tended to break off near their bases rather than be pulled completely free.  This means that there is a possibility that some spiders may still remain in the cones even after they've been peeled.  However, the peel method has been effective in dislodging additional spiders from previously tapped cones, so it's effective to some degree.

Below are a few photos to help you visualize what I'm describing.

Here's a photo showing what a typical peeled ponderosa pine cone looks like.  Notice the silken spider refugium that I've drawn a circle around.  In the case of this particular cone, tapping it hadn't expelled the spider resting inside that refugium.  Subsequently peeling the cone didn't force the spider out either, but it did make it possible for me to spot it, open it and collect the spider.

This spider refugium and its inhabitant were only visible to me after I peeled the cone.

Peeling occasionally exposed tiny refugia between a cone's tightly-packed basal scales.  I never found any of them inhabited.  Was that because they were vacant before I picked up the cone, or because tapping had already expelled their inhabitants?  The mystery remains.

Tiny, empty refugium exposed by peeling.

 If I've left any questions unanswered or any points unclarified, or if you have ideas for building a better mousetrap, please feel free to drop me a note in the comments.