Acorn weevils are fascinating insects that feed primarily on acorns, as their name suggests.
These fascinating beetles are brown in color and have a distinctive long, thin snout, which they use for boring into acorns to lay their eggs. They have a curved body, tapering towards both ends and grow up to about 3/8 inch long.
What Is an Acorn Weevil?
The Acorn Weevil, or Curculio sp., is a small, brown beetle belonging to the order Coleoptera, the family Curculionidae, and the genus Curculio1. Key attributes of this insect include:
Acorn Weevils undergo a complete life cycle, consisting of egg, larva, pupa, and adult stages.
The female nut weevil lays her eggs inside developing acorns, hickory nuts, or other similar nuts, by boring tiny holes with her slender snout3.
Once hatched, the pudgy, legless larvae feed on the nutmeats before boring their way out4.
These larvae then drop to the ground and burrow into the soil to spend one to two years before pupating and emerging as adults5.
As part of the Curculio genus, Acorn Weevils are found around the world. They are primarily found in regions where oak trees and other nut-producing trees grow in abundance.
Specific species like Curculio glandium can be found in certain geographical areas, each with a preference for different types of nuts.
The Impact of Acorn Weevils on Trees
Acorn weevils are insects notorious for infesting the acorns of oak trees.
These weevils have long, slender snouts called rostrums. They come in the brownish color and varied patterns1.
Female acorn weevils have longer rostrums compared to their male counterparts1. During their lifecycle, the adult weevil lays eggs inside green acorns4.
After hatching, the larvae feed on the acorn’s interior, having a detrimental effect on the tree’s reproductive ability4. Once the acorns fall to the ground, the larvae emerge, burrow into the soil, and continue developing4.
In oak trees, the impact of acorn weevils can cause:
While information regarding the direct impact of acorn weevils on hickory trees is scarce, nut weevils, in general, can affect hickory nuts.
Nut weevil larvae are legless grubs that feed on the interior of nuts, much like acorn weevils2.
The larvae of nut weevils have similar effects on hickory nuts and trees. These include:
Acorn weevil infestations can be identified by observing the acorns themselves. Damaged acorns may have:
Holes: Small, perfectly round exit holes created by weevil larvae
Color: A faded or darker appearance, signaling internal damage
Mealy texture: The inside of the acorns might appear mealy and dark brown, a sign of insect activity
Table Showing The Differences Between Healthy And Infested Acorns
Small, round holes
Mealy, dark insides
Identifying Weevil Larvae and Grubs
The larvae of acorn weevils, also known as grubs, have distinct characteristics:
Size: Grow to about 3/8 inch long
Shape: Curved, tapering toward both ends, fatter in the middle
Color: Creamy white, with a brown head
For example, when opening an infested acorn, you might find a grub-like larva that has been feeding and causing damage.
Comparison of Acorn Weevils and Chestnut Weevils:
While adult acorn weevils are about 3/8 inches long with a long, thin rostrum, chestnut weevils are slightly larger, reaching up to 1/2 inch in length. Both types of weevils feature rostrums that they use to bore holes and lay their eggs in the nuts.
3/8 inch long
Up to 1/2 inch long
Long, thin rostrum
Long, thin rostrum
Creamy white with brown head
Similar to acorn weevil larvae
Weevil larvae, regardless of the type, pupate in the ground before emerging as adults. Detecting an infestation early can help in preventing further damage to the acorns or other nuts.
Controlling Acorn Weevils
Acorn weevils can be managed through various cultural practices. One effective method is to collect acorns in the fall, as it helps reduce the number of larvae that survive during winter.
Insecticides and Pesticides
Using insecticides and pesticides can help control acorn weevil populations by targeting adults or larvae. Keep in mind that:
Some insecticides may have a negative impact on the taste of acorns.
Be cautious when using chemicals, as they can also affect other species, such as squirrels.
Acorn weevils have natural predators that can help reduce their numbers. These include rodents, which are common in North America and Europe.Table showing the pros and cons of different acorn weevil control measures
Effective in killing weevils
Can affect taste and harm other species
No chemicals needed
Reliance on other species
Acorn Weevil and Human Interaction
The Acorn Weevil (Curculioninae) is a small insect that can affect the quality of acorns collected during autumn for human consumption.
They are considered a pest due to their larvae tunneling into acorns, rendering them useless. Here are some tips to consider when collecting acorns:
Collect acorns in September, before heavy rains or after the weevil has emerged
Discard acorns with tiny holes, indicating weevil presence
When it comes to managing Acorn and Nut Weevil populations, consider these methods:
Regularly clean up fallen acorns to reduce habitat for reproduction
Introduce natural predators, like birds and rodents, to the area
Effects on Wildlife and Ecosystems
Acorn Weevils can impact the ecosystems as they reduce food source for other wildlife. While collecting acorns, you might notice some of the following characteristics in infected acorns:
Acorns that feel lightweight due to tunneling
Tiny holes on the surface
Acorn Weevils can make it challenging to gather and store acorns for human consumption. Proper collection techniques, identification, and management methods can help mitigate the effects of these insects.
Acorn Weevils play a significant role in the ecosystems where oak trees and other nut-producing trees thrive. Their life cycle, reproductive habits, and impact on tree health and seed production highlight their ecological importance.
Understanding the signs of infestation and implementing control measures, such as cultural practices and natural predators, can help mitigate their effects.
By managing Acorn Weevil populations, you can maintain the balance of wildlife food sources.
The Acorn Weevil is one of the most famous insects that our readers talk about and ask to know about. Over the last two decades, we have received dozens of emails from our readers asking us to identify this beautiful insect.
We have reproduced some of the best ones with some beautiful images for you to have a look.
Letter 1 – Acorn Weevils Mating
mating acorn weevils
HI BUGMAN!! I love your site!! It’s helped me identify lots of insects and has only helped my already huge interest in bugs. I have been having a problem with acorn weevils on my pin oak tree in Columbia MO… so they pose a threat to the tree? attached is a picture of two of them mating. THANKS!!
Thanks for sending a new species to us. The Acorn Weevil, Curculio glandium, can be quickly distinguished by the elongated snout or rostrum. We have located information that the Acorn Weevil does not pose a threat to the oak tree itself as both adults and larvae feed on the acorns. We apologize for not having the ability to respond to every letter you have written to us, and if there is anything that is either new to our site or a pressing matter for you, please resend those letters and images.
Letter 2 – Acorn Weevil
My name is Matthew Frias, I am a 16 year old high school senior. I would like to ask for your help with identifying a strange bug. Today, I came across a strange looking bug that had a striking resemblance to the kiwi bird (well, to me at least) I have never seen this bug before in my life. I found this bug sitting on my nightstand in my room. It walks very slowly and has the ability to fly. The long apendage coming from its head seem like it is used to feed on sugar food (flowers perhaps?) I tested this by giving it a bit of sugar-water. It doesn’t seem to be dangerous since i’ve picked it up before. Also, the apendage coming out of its head seems to have two antenae attatched to it. They come out a little less than half-way from the face. I have attached a sample picture of the bug. If you need more samples I have other pictures at different angles. Yet I feel this is one of the best angles I could get with my camera. Thank you very much.
This is an Acorn Weevil in the genus Curculio. The California Acorn Weevil is Curculio uniformis, but we cannot quickly locate an image nor the range. That species is still our best bet.
Letter 3 – Acorn Weevil
Acorn Weevil pics for you plus my gratitude
I found you last week when I wanted to know what beautiful
bug was crawling on my kitchen bowl. Thanks to you I
discovered it was an Assasin Bug(pselliopus barberi) and a
whole new world was opened up to me. I had never even
heard of an Assasin bug before. Now I am a little addicted
to finding bugs in my yard and trying to identify them.
I guess I love the challenge, and it’s terribly fun to find
a match and put a name with the buggy face. I’ve been
using your site and the BugGuide. Thank you so much
for a wonderful and facinating resource for the bug illiterate.
My kids love it, too. We are working on creating science
journals this year, and our bug finds with proper identification
are a great addition! I thought you might like to have
some pictures of our Acorn Weevil. I noticed the one
you have is blurry. Also, I thought this was a pretty
picture of a Monarch Caterpillar. These were all taken
in my yard in Jefferson City, Missouri. I would like
to send other pictures just for fun, but only if you want
them. I know you get so many. With much gratitude
Thanks so much for your Acorn Weevil photo. We are linking
to an interesting
website about Acorn Weevils in the genus Curculio.
Letter 4 – Acorn Weevil
Fri, Jan 23, 2009 at 5:59 AM
What kind of bug is this? Is it dangerous? I found it indoors about a week ago in our living room, on our couch.
oklahoma city, ok
This is an Acorn Weevil in the genus Curculio which can be verified on BugGuide. The snout is quite distinctive for Nut Weevils and Acorn Weevils.
Letter 5 – Nut or Acorn Weevil, we think
What is this thing?
October 25, 2009
I found this bug on the edge of my fishtank. It is now October 25th.
Hi Tree C.,
This is a Weevil, a member of the largest family of Beetles. Often exact identification from a photo is impossible. That said, we believe this is a Nut Weevil or Acorn Weevil in the Tribe Curculionini. There are several images that look similar on BugGuide, but they are not identified to the species level.
Letter 6 – Acorn Weevil
beetle thing with long beak
Location: Farmingdale, Long Island, New York
August 26, 2010 12:54 am
Dear Mr. Bugman,
I’ve been browsing your site and haven’t really found anything close to this little guy I found today. I work at an airport in New York, and I found him while I was pumping fuel into my fuel truck. It looks kinda like a beetle, but it has this really strange beak. The beak is thin and about the length of one of its legs. And it looks like it has two antennae (?) protruding from the beak. The insect itself is about a centimeter long, I would say. This is the strangest insect I’ve seen in a while. I really hope you get to this one because I really want to know what it is!
This interesting beetle is an Acorn Weevil in the genus Curculio. According to BugGuide: “Female uses her long snout for boring into nuts/acorns, and deposits eggs there. Larvae feed inside the acorn/nut and emerges to pupate in the soil.“
Letter 7 – Nut or Acorn Weevil
What on earth is this??
Location: Bensalem, PA
March 8, 2012 9:13 am
A friend of mine took a picture of this bug while he was at an ATM in Bensalem, PA. It was on the ATM itself. This was taken either at the end of Feruary or the beginning of March.
Signature: Bill O’Neill
This long nosed creature is a Nut or Acorn Weevil in the genus Curculio. According to BugGuide: “Female uses her long snout for boring into nuts/acorns, and deposits eggs there. Larvae feed inside the acorn/nut and emerges to pupate in the soil.”
Letter 8 – Acorn Weevil from Japan
Subject: Help a Bugger Out
Location: Tosa Peninsula, Kochi, Shikoku, Japan
May 15, 2014 6:17 am
Me and my boyfriend have been travelling in Japan now for 7 months. We came here originally for the birds but the huge variety of strange, colourful and giant insects have been stealing the show a bit.
This guy flew down off a tree, looking closely at its face we decided it was the funniest bug we had seen all trip, so that seems like a good place to start.
I would like to send more if that’s okay?
This is an Acorn Weevil in the genus Curculio, but our quick research did not determine which species are found in Japan. You can find information on BugGuide regarding North American species that might be helpful for you.
Letter 9 – Acorn Weevil
Subject: What the heck is this?
Location: Queens new york
September 9, 2015 12:14 pm
Help, this thing was on the wall, I live in Oakland gardens Queens NY and I found it. It has one long nostril or idk what that is. It has six legs and little suckered freaked me out when I learned it could fly! I don’t want to kill it if it’s not harmful. I’d much rather let it go, but I need to know if it’s harmful or not. Please get back to me soon!
Signature: Freaked out human
Dear Freaked out human,
Does the Oakland Gardens have many of its namesake oak trees nearby? This is an Acorn Weevil and we believe it inadvertently entered your home.
Letter 10 – Acorn Weevil
Subject: I can’t identify this bug
October 5, 2015 9:53 pm
This bug was in my friend’s hair and I must know what it is. Is it some type of weevil?
This is indeed an Acorn Weevil or Nut Weevil in the genus Curculio. Finding it in your friend’s hair seems purely coincidental. According to BugGuide: “Female uses her long snout for boring into nuts/acorns, and deposits eggs there. Larvae feed inside the acorn/nut and emerge to pupate in the soil.”
Letter 11 – Acorn Weevil
Subject: Never saw this one before
Geographic location of the bug: Oklahoma City
Time: 07:45 AM EDT
There were several of these in a Porta pot for about 5 days. They can fly too.
How you want your letter signed: Jeff
This is an Acorn Weevil or Nut Weevil in the genus Curculio. According to BugGuide: “Long slender beak; body robust. In some species, female snout may be longer than the body (never in males).”
Letter 12 – Acorn Weevil
Subject: Really weird and really scared
Geographic location of the bug: sherman, texas
Time: 08:30 AM EDT
Your letter to the bugman: This thing landed on my arm in my office and i have no idea what it is. I didn’t feel any bite, all I felt was it land on my arm, and i brushed it off immediately. I just need it identified to know if I’m in danger of a parasite, infection, virus or otherwise transmittable illness. It has what I can only assume to be some form of proboscis and an empty white container on its “abdomen” with a grey/black and brown color and a somewhat fuzzy appearance. It also had a triangle-like shape when viewed top down.
How you want your letter signed: Gerald
This appears to be a very dead Acorn Weevil or Nut Weevil. You need not fear “danger of a parasite, infection, virus or otherwise transmittable illness” from a harmless Acorn Weevil.
Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.