The locust borer beetle is a type of long-horned beetle, known for its distinctive yellow and black markings, as well as its infestations in black locust trees. While these beetles have a striking appearance, many people might wonder if their bite is something to be concerned about.
Although the adult locust borer beetle closely resembles wasps or hornets because of its bright yellow markings, it is not poisonous or capable of stinging. In fact, these beetles are mostly harmless to humans, focusing primarily on feeding on the pollen and nectar of goldenrod plants. So, there is no need to worry about any adverse effects or dangers related to their bite.
It’s worth noting that locust borer beetles do pose a danger to black locust trees, as their larvae tunnel into the tree trunks, causing significant damage. Management of infestations typically requires pruning infested branches and applying appropriate insecticides, to maintain the overall health of the trees.
Locust Borer Beetle Bite: Is it Poisonous?
The Locust Borer (Megacyllene robiniae) is a type of long-horned beetle. As adult locust borers feed mostly on the nectar and pollen of goldenrod plants, they aren’t known to be harmful toward humans1. Their larvae, however, can cause damage to locust trees2.
Some key features of the locust borer beetle include:
- Adults are about one inch long with reddish legs1
- Distinct yellow and black bars found on their heads, pronotums, and elytra2
When discussing whether a locust borer beetle bite is poisonous, it’s important to note that:
- There’s no information suggesting that a locust borer bite contains any venom or toxins
- Bites from locust borers are rare, as they primarily consume plant material1
In comparison to other beetle species, locust borers have some notable differences:
| Characteristic | Locust Borer | Other Beetle Species |
|---|---|---|
| Coloration | Yellow & black bars1 | Varies widely |
| Habitat | Goldenrod plants1 | Various locations |
| Effect on humans | Not poisonous | Some species can deliver harmful bites |
In summary, locust borer beetles do not possess a poisonous bite, nor do they pose a significant threat to humans. Their primary focus lies in plant consumption, more specifically on goldenrod plants.
Classification and Identification
The Locust Borer Beetle (Megacyllene robiniae) is a species of longhorn beetle belonging to the Cerambycidae family within the order Coleoptera. It is primarily known for infesting black locust trees (Robinia pseudoacacia). The adult beetle can be identified by its distinctive features:
- Black and yellow markings mimicking stinging insects
- Yellow “W” shape across the elytra or wing covers
- Reddish legs
- Antennae that are about as long as their body
These beetles are not known to be poisonous and do not possess any venom. In comparison to other beetles, the locust borer has some unique features:
| Feature | Locust Borer Beetle | Other Beetles |
|---|---|---|
| Body Markings | Yellow and black | Various colors |
| Leg Color | Reddish | Various colors |
| Antennae Length | As long as body | Varies, often short |
When it comes to identifying the locust borer, remember these key points:
- It belongs to the Cerambycidae family
- Mimicking pattern helps protect from predators
- Infests black locust trees specifically
- Not venomous or dangerous to humans
Habitat and Life Cycle
The locust borer beetle (Megacyllene robiniae) is native to North America, specifically in the eastern part of the continent1. In the early 1900s, they spread to Canada2. These beetles prefer habitats such as:
- Uncultivated fields
- Meadows
Locust borers rely on plants like goldenrod (Solidago) for nectar and pollen3. Their life cycle consists of three main stages4:
- Larvae
- Pupa
- Adult
During winter, the beetle larvae hibernate within the tree bark5. In spring and summer, they feed on the tree’s heartwood, causing structural damage6. Eventually, the larvae pupate and transform into adults7.
Populations of locust borer beetles can vary depending on factors like geography, climate, and food availability.
Comparison Table
| Locust Borer Beetle Stage | Characteristics |
|---|---|
| Larvae | Legless, white, tunneling |
| Pupa | Protected, metamorphosis |
| Adult | Black, yellow markings |
Host Plants and Damage
The locust borer beetle is known to infest and damage black locust trees and its cultivars, such as the purple robe locust1. Feeding primarily on tree xylem1, these pests can weaken branches or trunks through extensive tunneling in the wood1.
Infestations can leave trees more susceptible to wind damage, hinder the flow of nutrients, and allow entry points for pathogens2. Both the larvae and adult beetles can cause harm to trees, with the life cycle disrupting the tree’s health and growth1.
Some damage signs include:
- Holes in the bark
- Reddish frass in bark crevices or around the base of the tree2
Insecticides can provide some control, but proper tree care and maintenance are also essential to prevent infestations3.
Comparison of infested vs. healthy trees:
| Infested Trees | Healthy Trees |
|---|---|
| Holes in the bark | Intact bark |
| Reddish frass | No visible frass |
| Weakened branches | Strong branches |
| Prone to wind damage | Resistant to wind |
| Nutrient flow hindered | Nutrient flow maintained |
Prevention and Management
Locust borers are a type of long-horned beetle that can cause damage to trees, especially black locust trees. Although they are not known to be poisonous, it’s essential to manage them to maintain the health of your trees.
To prevent locust borer infestations, focus on maintaining the overall health of your trees. Ensure they receive adequate water, especially during drought periods. Also, prune any infested branches and either chip or burn them to eliminate the pests.
When choosing insecticides, opt for carbaryl (also known as Sevin) or pyrethroid-based treatments. Apply these insecticides as a residual surface application on the bark of the trunk and large scaffold branches during late July or early August, before egg-laying begins.
Some pros and cons of using insecticides include:
Pros:
- Effective at reducing borer populations
- Can stop an infestation from spreading
Cons:
- May impact non-target species
- Can be harmful if not used correctly
It’s essential to monitor for locust borer activity regularly. Examples of signs of infestation include frass (sawdust-like material) near the tree base, blistered bark, and exit holes on the trunk.
To recap, the key elements for locust borer management are:
- Maintain healthy trees with proper watering and pruning
- Apply appropriate insecticides before egg-laying
- Monitor for signs of infestation
By following these steps, you can prevent or manage locust borer infestations and maintain the health of your trees.
Footnotes
- Locust Borer – Home and Garden IPM from Cooperative Extension ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10
- Locust Borer – Department of Entomology ↩ ↩2 ↩3 ↩4 ↩5
- https://extension.umaine.edu/home-and-garden-ipm/fact-sheets/common-name-listing/locust-borer/ ↩ ↩2
- https://extension.usu.edu/pests/ipm/ornamental-pest-guide/arthopods/wood-borers/locust-borer ↩
- https://extension.usu.edu/pests/ipm/ornamental-pest-guide/arthopods/wood-borers/locust-borer ↩
- https://extension.usu.edu/pests/ipm/ornamental-pest-guide/arthopods/wood-borers/locust-borer ↩
- https://mdc.mo.gov/discover-nature/field-guide/locust-borer ↩
Reader Emails
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.
Letter 1 – Locust Borer
What is this Bug
I found this bug on the locust tree in my back yard. There is quite a few of them on the tree. Have you any idea what it is?
R. B. Rogers
Hi R.B.,
The Locust Borer, Megacyllene robiniae, is a beetle. The larvae bore in the wood of black locust trees and adults are often found on goldenrod in the fall.
Letter 2 – Locust Borer
Interesting beetle found on Sunflowers
A while back, sry i dont remember the date, I was looking on our sunflowers for interesting bugs and luckaly found one. It was a large beetle, about the length of an adult yellow jacket, and was also camaflauged like a yellow jacket. it seemed a convenient ploy, since there were many wasps flying around the sunflowers. I was wondering if you might now what it could be. I’ll try to send a picture when I get home.
Thank you!
Kyle
Hi Kyle,
Just as we suspected before you sent the photo, this is a Locust Borer, Megacyllene robiniae. The grubs bore into the wood of black locust trees and adults are found on flowers, especially goldenrod.
Letter 3 – Locust Borer
Bug ID
Hi,
My uncle, who takes awesome pictures of bugs took this. I am stumped. It looks true buggish. What do you think?
This is a Locust Borer, a Cerambycid Beetle. The adults are pollen feeders and are attracted to goldenrod.
Letter 4 – Locust Borer
NW Indiana Sugar Maple Borer?
From NW Indiana again, and saw this guy doing a backstroke in the pool. As I usually try to give everyone a fair shake, I rescued him and got a few quick pics before he headed off. Now I review the site and it looks like this guy may be a Sugar Maple Borer; if so was I too quick in releasing him? By your description this may be one of the more harmful beetles in an area and its discovery may be of some concern…
M
Hi M,
Right family, wrong species. This is a Locust Borer. Grubs bore in the wood of black locust trees and pollen and nectar feeding adults are often found on goldenrod. Adults emerge in the fall.
Letter 5 – Locust Borer
Locust Borer on goldenrod.
Hey bugman,
I think its really cool that the Locust borer is the new bug of the month for October. I have seen several this season and taken some pictures. This is the best one. Hope you enjoy it as much as I enjoy your website, which is a lot!
Mike D
Hi Mike,
Adult Locust Borers are active in the fall, and are commonly associated with goldenrod where they feed on nectar and pollen..
Letter 6 – Locust Borer
A Locust Borer Beetle
Hi Daniel,
I couldn’t find this lovely beetle on your site, but s ome research led me to Megacyllene robiniae . It’s pretty similar t oMegacyllene caryae (which I did find on your site) ,but the yellow stripes seem more pronounced. Evidently this striking bug is pretty common this time of year, but this is the first time I’ve ever seen one. It was nearly an inch long and was hanging out on the goldenrod, along with a bunch of Pennsylvania leatherwings. It’s always so exciting to spot something new in the backyard, and I just wanted to share. Keep up the good work! Regards,
Christina
New Lenox, IL
Hi Christina,
We actually do have images on Locust Borers on some of our 15 pages devoted to beetles. This would have been an excellent choice for Bug of the Month for September, but we already picked the Bagworm since there were so many recent requests for identifications. Locust Borers are strikingly beautiful beetles that are commonly found on goldenrod where they feed on the pollen.
Letter 7 – Locust Borer
Please ID this beetle found on Cape Cod
I found several beetles like this in a patch of flowers in a saltwater marsh on Cape Cod. There were lots of aggressive wasps around the flowers that chased off bees and other insects that approached (and me!), but these beetles were left alone. I have never seen this beetle before, and I’d like to know what it is. Also, is the black and yellow coloration a strategy to fool the wasps into accepting their presence?
East Sandwich, CApe Cod, MA
Tim Crowninshield
Hi Tim,
What a positively gorgeous photo of a Locust Borer. These wasp mimic beetles are found in the late summer and early autumn, and they are frequently associated with goldenrod blossoms. Their coloration helps them fool potential enemies.
Letter 8 – Locust Borer
Subject: black/green striped beetle
Geographic location of the bug: Walla Walla, WA
Date: 09/18/2018
Time: 09:26 PM EDT
Your letter to the bugman: Hello, we found this inch-long beetle on a lemongrass plant in our yard. It’s not in any of our guidebooks. What is it?
How you want your letter signed: Beetle-befuddled
Dear Beetle-befuddled,
This is a Locust Borer, and if your guidebooks are Pacific Northwest local, and not published very recently, they probably don’t include this distinctive beetle because it has recently expanded its range of eastern North America because of the cultivation of its host tree, the black locust. According to BugGuide: “Previously confined to the native range of Black Locust in the northeast, it has spread with the trees throughout the US and parts of Canada. Black Locust is used for reclamation and similar projects where trees are likely to be stressed and thus more vulnerable to damage.”
Letter 9 – Locust Borer
Subject: Yellowjacket or Cricket?
Geographic location of the bug: New Jersey
Date: 09/22/2019
Time: 08:48 PM EDT
Your letter to the bugman: This bug landed on me and later seemed to “fly” away like a grasshopper. It wasn’t behaving like a wasp and it’s head and body shape don’t look wasplike. What is it???
How you want your letter signed: Libby
Dear Libby,
This Locust Borer is actually a beetle that is a very effective Yellowjacket mimic. Locust Borers are often found on Goldenrod.
Letter 10 – Locust Borer
Subject: Weird bug on sunflower
Geographic location of the bug: Bay Shore, New York
Date: 09/04/2021
Time: 04:59 PM EDT
Your letter to the bugman: Saw this yesterday on my sunflower.
How you want your letter signed: Jimmy R.
Dear Jimmy,
The Locust Borer is a Beetle but it is a very effective mimic of a Yellow Jacket, a stinging Wasp. We often get images of Locust Borers near the end of summer and they are especially fond of goldenrod.
Letter 11 – Locust Borer in Oregon
locust borer
Location: NE Oregon
October 9, 2011 9:10 pm
I found this bug in my yard and found out it is a locust borer similar to the hickory borer but we do not have the trees i read that it lays its eggs in. I have all kinds of trees around us. but none like it said this thing likes. We are in the inland pacific northwest and even your report says they are not native to here. how do we protect our trees from them?
Signature: worried about this bug
Dear worried about this bug,
As you letter indicates, the Locust Borer, Megacyllene robiniae, is native to the eastern portions of North America, however, with the cultivation of its larval food plant, the black locust, as well as the more decorative locust cultivars, the range of the Locust Borer has expanded to the Pacific Northwest. The BugGuide data map shows states that include sightings submitted to that website. You do not need to worry about other trees as the Locust Borer is host specific to Locust trees.
I found 2 locusts in my yard today I haven’t seen these in 35 years and when I did see them I lived in AZ… this has come as a big surprise as I have been in oregon for 35 years and have never came across one until today. Does anyone know how we can all of a sudden find locusts here?
Locusts are Grasshoppers, and this Locust Borer is a beetle that feeds on BlackLocust Trees, hence the name. According to BugGuide, the Locust Borer, is reported from Oregon bug NOT Arizona, but Oregon and the Pacific Northwest is not the native range of the species because according to BugGuide: “Previously confined to the native range of Black Locust in the northeast, it has spread with the trees throughout the US and parts of Canada.” We suspect you saw the similar looking Mesquite Borer in Arizona, and according to BugGuide: “Adults are active day and night, running rapidly along freshly cut branches of their host plants and feeding on the blossoms of Koeberlinia, Acacia, Baccharis, Bumelia, Clematis, and Solidago.”
Hi folks well all I can say is yes the Locust borer beetles are definitely here and I’m in Washington right across the river from Portland Oregon in Vancouver Washington..
We have LOTS of locust trees here, and the beetles too. If they are chewing up the trees, no wonder so many branches come crashing down during a wind storm! I have seen several of these beetles this summer, but never seen them before. Colorful bugs for sure!
Hi folks well all I can say is yes the Locust borer beetles are definitely here and I’m in Washington right across the river from Portland Oregon in Vancouver Washington..
We have LOTS of locust trees here, and the beetles too. If they are chewing up the trees, no wonder so many branches come crashing down during a wind storm! I have seen several of these beetles this summer, but never seen them before. Colorful bugs for sure!