I've already posted about what made the holes in these acorns, so now let's take a real close look at sealed holes and then the caterpillar that made the windows.
There seems to be an additional substance coating the silk webbing... perhaps wax that acts as waterproofing. I launched a half of an acorn shell which has a sealed hole in the bottom... as you can see the seal lets no water in. The acorn boat has not taken on water for an hour or two.
I don't know that the function of the seal is to keep out water... I suspect that the main purpose is to keep out unwanted guests. There are plenty of other insects that will invade an acorn, so perhaps the window encourages them to seek out other acorns
This photo shows a microscopic view of the material that was used to cover the hole in the acorn. I used oblique lighting to highlight the silk strands that seem to trend in one general direction - perhaps one layer?
Actually there are many criss-crossing layers of silk strands...see this next photo of a microscopic view (at very high magnification) looking at the silk window.
The Acorn Moth caterpillar's job of spinning its curtains looks similar to what paper or cloth looks like under the microscope.
Here is another photo of the Acorn Moth caterpillar's silk creation... taken with oblique lighting to accentuate the layering.
In our experience, this time of year the acorns with the sealed holes were occupied by a small, white caterpillar - the larva of the Acorn Moth, Blastobasis glandulella. Here is a photo of a cut-away of an acorn showing the Acorn Moth caterpillar on its frass pile inside the acorn.
Here is a photo of the Acorn Moth caterpillar.
|Acorn Moth Caterpillar|
Here is another photo of the Acorn Moth caterpillar - one that refused to stay on its feet for the picture.
This photo shows a cut open wormy acorn. The Acorn Moth caterpillar is visible near the top center of the acorn... it is partially sticking out of one of its tunnels.
hole was made by an exiting acorn weevil? Later, an Acorn Moth layed an egg in the hole and, well, soon enough there was a wormy acorn with silk curtains.
All seriousness aside, let your imagination drift through the oak forest at twilight...
Its fall, and the forest floor is blanketed with leaves and peppered with many fallen acorns. Many of those nuts have tiny, silk-curtained windows. I like to imagine the acorn dwellers turning on lights inside their snug abodes.