Turning Over A Log

If you're looking for creepy crawly things, supposedly a pretty reliable way to find them is to turn over a rotting log. I have had some success with this method; of the two salamanders I have seen in my backyard in the 19 years since we bought this piece of the planet, one of them was found when we turned over a rotting log. And there are a couple of random pieces of lumber in the backyard leftover from building projects that have never been dealt with, and when I look under those I can usually find something from the arthropod world. But there is one particular rotting log next to one of my backyards wooded paths that has always been strangely useless in this regard. It's a pretty old, rotted log; I don't even know how long it has been there. Sometimes on my bug walks I nudge it over with my foot to see if there's anything interesting underneath, but most of the time I don't see anything at all. Once last summer I saw a pile of squirming earthworms under there, and since I am grossed out by earthworms I didn't want to look under there again for a long while. I did look under there yesterday, and saw nothing. But today...

Backyard Bug of the Day:

I am pretty sure that this is a winter firefly larva. I think this because a) this is what beetle larva sometimes look like, b) it looks kind of like a winter firefly, to the extent that a beetle larva looks like an imago (adult) beetle, which is to say not much, but it does definitely look like if it is going to grow up to be a beetle, that is the kind of beetle it will grow up into, and c) I looked winter firefly larvae up on the internet, and there were a lot of pictures that looked like this, and even though the internet is not a reliable source for insect identification in my experience, it is the best I can do because my various insect field guides generally don't show larvae/nymphs. I wish I had found a winter firefly today, basking on a tree, so I could post a picture to compare them, but alas, I still can't find any. Which makes it feel a bit ironic to me that I found a larva, because those are much harder to find. In fact, this is the first one I have ever seen. I believe that the tail end (which is on the left in the picture) is bioluminescent, but it was sunny daytime, so I don't know for sure). Winter fireflies are diurnal as adults and no longer have bioluminescence, but the larvae light up. Not that I have seen one do this.

The head end.

Oh, look, a photobomber.

So, there were actually quite a few insects and other arthropods to be found under that log today. Here's three, with the winter firefly larva kind of curled up. I saw a couple of other millipedes (or centipedes, or some other similar thing, those are definitely not my area), too, but they scurried into hiding pretty fast.

Insects have little regard for personal space.

I found a couple of these tiny hoppers under the log, too, which was pretty unexpected.

So what I want to know is, why haven't I seen any or all of these insects on the other occasions lately when I turned over that log? Where they not there? Were they too well secreted into the nooks and crannies? Today was warm (almost 50ºF), but there have been other days as warm when I have looked under there. It is puzzling.

I did my entire usual bug walk, and the only other insect I found, besides more flies basking on the side of the house, was this:

Birch catkin bug, actually on a black birch tree.