A caller to the GardenLine radio show last weekend was very concerned about his oak tree covered in spider webs.

My first question was if the webbing was in the leaves or smaller branches. He said no, it was only on the trunk and larger branches.

Although I knew right away the cause was bark lice — and they're beneficial insects — I was honestly caught a little by surprise because I have not had a question about them in over two years. I commented on the air to my producer that he should be prepared ... bark lice are cycling back, and we are going to get this question over and over again for a couple of months.

And sure enough, since Monday I've seen a dozen emails on the same subject. Here's an example from Alex:

I have a tree, sorry I don't know what type it is, that has webs around the big branches. I read your tip sheet regarding web worms. I think this is my problem, but I am not sure since the webs are not in the leaves of the tree but are building around the branches. Especially where the branches form a "corner." Is there any way to determine what is happening?

Alex was right and wrong! Wrong, because it wasn't web worms! Web worms can actually be harmful to trees. This is a perfect description of bark lice, especially the part about "where the branches form a corner." The beneficial insect is actually cleaning up the bark of the tree. For Alex and everyone else experiencing this phenomenon, here's what I've written about bark lice and their webs previously:

"Bark lice appear suddenly, and frequently overnight. You walk out to get the morning paper, and there they are. Just yesterday, that same tree looked perfectly normal.

"Put away any insecticide or garden hose you may tempted to spray on this unique garden critter. It may seem hard to fathom, but bark lice are not a threat to the tree in any way, and they will disappear just as mysteriously as they appeared in a couple of weeks."

The bark louse's favorite target is rough-barked hardwoods. The little critters are beneficial because they scour the bark for fungi, spores, pollen, lichen and other debris. While dining, they spin a web for protection. Once they are done with a tree, the web usually disintegrates within a week.

Bottom line: you don't need to do anything. In fact, if you try to spray the web with an insecticide, it will bounce right off. And if you do penetrate the webbing, you'll be destroying a beneficial insect. So, enjoy the creepy web. In fact, peek in and take a closer look at the tiny army working underneath.