If you’ve ever seen a perfect tiny hole on an acorn, you’ve probably encountered an acorn weevils‘s nursery.
“Acorn weevils are immediately distinguished by their incredibly long mouthparts called a rostrum, and in some species, these can be almost as long as the weevil’s own body. At its tip, there is a serrated edge, allowing them to cut through even the toughest plant material.
“They will spend most of their adult life wandering around their tree, foraging for food, looking for florets, galls, and even acorns.”
“Their strong, sharp rostrum lets them bore through woody outer tissue to get to the soft, nutritious flesh inside, which they suck up as if using a straw. But toward the end of the summer, as the acorns start to ripen, the weevil’s behavior changes…”
Travel up into the branches and leaves of an oak tree, where small, mottled brown insects, around 4 to 8 millimeters long, spend their entire lives. This Team Candiru video shares how these common insects of Europe and North America use their beaklike mouths to eat and create a space for their eggs inside acorns.
Inside, the weevil grubs eat and grow until fall when acorns drop to the ground. The grubs then chew their way out and burrow into the soil where they pupate for one to five years. When they emerge as adult weevils in the warmer months, they climb back up into the oaks and repeat the cycle.
When gathering acorns, be sure to examine them for pinholes, which may indicate insect activity. Acorns with pinholes can be returned to where they were found.
Related on iNaturalist: Photos of Nut and Acorn Weevils.
Watch these related weevil and acorn videos on TKSST:
• The Giraffe Weevil – BBC Madagascar
• A leaf-rolling weevil crafts its nest with careful folds
• The Anomalies: The Acorn Woodpecker
• From seed to sapling: Time-lapse of an oak tree
• Acorn by Madeline Sharafian