It turns out those little holes are drilled by a weevil. An acorn weevil, specifically. You know, those little holes in, well, acorns.
Until recently, I didn’t know that.
The cause of those tiny openings has been a mystery to me for the longest time. Sure, it’s been one of those mysteries that could be solved with a simple internet search, but, as is so often the case, when I’ve thought to search I’ve been away from a computer, and when I’m with a computer I don’t think to search. Classic situation.
Anyway, I just recently came across the answer, and I wasn’t even looking for it. The page was turned, and there it was. The book in hand was Douglas Tallamy’s The Nature of Oaks: The Rich Ecology of Our Most Essential Native Trees. The acorn weevil and its life cycle is addressed in “November,” the second chapter in the book.
The acorn weevil, I learned, is a small insect with an endearingly long rostrum, nearly the length of its body, that it uses to chew a small hole in an acorn. It then lays an egg or two in the hole, plugs the opening with dung, and moves on to the next acorn to repeat the process.
After hatching a few days later, the weevil larva burrows into and eats from the acorn until the nut drops in the fall. It leaves through hole in which its egg was first introduced, and burrows into the ground where it stays for a year or two before emerging as an adult to repeat the process with its own offspring.
As is the case with most insects, the weevil’s survival strategy as a species is based on quantity: Acorn weevils lay a lot of eggs in a lot of acorns.
As is the case with most trees, the oak’s survival strategy as a species is based on quantity: Oak trees produce a lot of acorns, only some of which are destined to be a weevil nursery.
A quick aside: What do bluebirds, wrens, chickadees, nuthatches, woodpeckers, and a host of other backyard birds have in common? They’re all insect eaters! Each of these birds would love nothing more than to find a juicy caterpillar, a scurrying beetle, or – yes – a long-nosed acorn weevil crawling along a tree branch.
These beloved birds need the acorn weevil for their own survival, so it’s a good thing there are so many of them available to meet for lunch.
I really like birds, so I have to confess I felt a pang of dismay when I went to the Internet to learn more about the acorn weevil.
Stick with me – I’m about to explain.
A search for “acorn weevil” brings up a number of sites providing information on “pest control” for the homeowner.
You see, the thing is, the acorn weevil doesn’t harm the tree. The acorn, yes, but not the tree. Unless you’re one of a very few people who use acorns to make flour, it’s just not a big deal to leave the bugs alone.
The bluejays will thank you.