This Weevil Has Puppet Vibes But Drills Like a Power Tool
This fuzzy acorn weevil can’t crack open acorns like a woodpecker or chomp through them like a squirrel. Instead, she uses her incredibly long snout, called a rostrum, to power-drill through an acorn’s tough and resilient shell. And it’s not just lunch on her mind – she’s also making a nursery for her babies.
TRANSCRIPT
The acorn weevil is fuzzy, tenacious and hungry. But what stands out the most is its supersized, skillful snout.
It’s called a rostrum, and it’s perfect for digging into the acorns brimming from these California oak trees.
See the acorn weevil right there? It blends right in.
She uses her sensitive antennae to sniff and taste her way to the perfect acorn.
She goes for the soft green ones. This one is too hard. This one’s too bitter! This one’s just right.
Her antennae don’t stick out right from her head; they would never reach the acorn. Instead they’re down here.
Her razor-sharp mouth sits at the very tip. She makes tiny cuts in the acorn’s surface to break through the hardest part of the nut. Once it’s weakened, she punches through.
The rostrum’s downward curve lets her bite into the acorn directly beneath her. She often digs in under the cap. Maybe it’s easier to grab on there, or softer underneath it.
Then, she bores in. Rotating her head and using her snout as a drill. She chows down as she goes.
When her antennae start to get in the way, no problem. She just tucks half of each one into these side channels called scrobes.
Inside, she creates an arrow-straight tunnel. The naturally arched rostrum straightens as it drills.
It can do this because the rostrum has two layers: a hard and thin outer cover, called the exocuticle, and a flexible and thick inside, the endocuticle.
You might be wondering: Where are the males? They’re here too. You’ll know them by their short rostrum. But that’s OK. They’re only tunneling into acorns for food. A female sports a rostrum as long as her body. Because she isn’t just eating. She’s building a nursery.
The deeper she digs, the safer her babies will be. After she’s done carving, she turns around and extends an egg-laying organ, her ovipositor. But it doesn’t just drop eggs. Its tip can smell and taste to make sure the environment will be suitable for her growing babies. Once she’s convinced, she deposits her eggs one by one.
But she still has more eggs to lay. And she can’t put them all in one basket. She lays her eggs all over the oak to increase the chance they’ll survive, drilling into dozens of acorns. But that’s exhausting. So sometimes, she tries to nab another weevil’s tunnel for her own babies.
This is mom vs. mom! Not this time! Go find your own acorn!
Over the next few weeks, the larva eats and grows. Once the acorns have darkened and matured, they fall to the ground. Using its powerful mandibles, the larva chews its way out of its safe home. That’s a tight squeeze!
Immediately, it burrows into the soil for protection. It will emerge in a coming season, waking up just as the new green acorns grow in the canopy above.
And then, the weevil will travel up the tree in search of its own perfect acorn, one that’s just right for its growing family.
Hey Deep Peeps! We’ve got more weevils for you. South American palm weevils are ready for their close-up, but their arrival could mean the end for California’s iconic palm trees. And PBS Terra has an awesome new insect series called — wait for it — Insectarium! Join invertebrate zoologist Dr. Jessica Ware as she explores insect habitats, meets bug enthusiasts, and visits incredible collections. Tell them Deep Look sent you!