Q: My little granddaughter recently picked up a few acorns and I tossed them on the dining room table. A week later, I was about to remove them when I noticed a fine acorn dust all over the table cloth and small white larva on the table and on the floor. What were these things and are they in all acorns?
A: Your acorns had acorn weevils in them. The insect overwinters in the earth but emerges in mid-summer. A female bores a hole in an acorn to deposit her eggs.
The larvae feed on the acorn nutmeat until autumn, then emerge right after the acorn falls from the tree. Your granddaughter must have found the acorns just after they fell.
You can determine with her which acorns are infested by putting them in a bucket of water. Nuts with larvae inside will float but uninvaded acorns will not.