Oil beetles, also known as blister beetles, are a common pest found throughout the United States and Canada. These insects can be easily identified by their elongated, narrow, and soft bodies, and they come in various sizes and colors link. An infestation of oil beetles can prove to be an issue for both gardeners and homeowners alike, as these pests can cause damage to foliage and also become a nuisance when they enter homes.
To effectively get rid of oil beetles, it’s crucial to understand their behavior and life cycle. These insects are attracted to lights and can often be found near windows and doors at night. Moreover, they lay their eggs in soil, and their larval stage causes the most damage to plants. By targeting these key aspects of their life cycle, we can employ various methods to eliminate the existing beetles and prevent further infestations.
In this article, we’ll explore different strategies that can be used to manage oil beetle populations, such as using sticky traps, introducing natural predators, and employing chemical control methods. Furthermore, we’ll discuss ways to limit their access to your home and provide tips for maintaining a healthy garden environment to discourage oil beetle infestations.
Overview of Oil Beetles
Description of Oil Beetles
Oil beetles, also known as blister beetles, are part of the Meloidae family. They are recognized by their elongated, narrow, cylindrical, and soft bodies. They have relatively short front wings, which do not extend over the tip of the abdomen.
Some characteristics of oil beetles include:
- Dark in color
- Range in size from 0.5 to 1.25 inches
- Visible part of thorax is narrower than head and abdomen
Species and Distribution
In North America, several species of oil beetles can be found. The most common species found in the United States are three-striped, grey, and black blister beetles. These beetles are distributed throughout the United States and Canada.
Common species in the United States:
|Three-striped Blister Beetle
|Identified by its three longitudinal stripes
|Grey Blister Beetle
|Grey in color
|Primarily Midwest and Eastern US
|Black Blister Beetle
|Black in color
|Various regions in the US
Damage Caused by Oil Beetles
Effects on Garden Plants
Oil beetles, belonging to the family Meloidae, can harm garden plants by feeding on their foliage and flowers. They may cause:
- Leaf damage: holes and skeletonizing
- Flower damage: petals and buds eaten
For example, oil beetles like the three-striped, grey, and black blister beetles are common in Nebraska and can cause significant harm to gardens.
Harm to Fruits and Trees
In addition to gardens, oil beetles may damage fruit trees and crops. Their feeding can lead to:
- Fruit damage: scarring and deformities
- Tree damage: weakened branches and reduced foliage
A comparison of common damage on fruit trees:
|Fruit Trees Affected
|Reduced market value, increased vulnerability to diseases
|Lower crop yields, unmarketable fruit
Impact on Home Interiors
While oil beetles are primarily outdoor pests, infestations can spread indoors. Effects on interiors include:
- Stained carpets and furniture from crushed beetles
- Unpleasant odors due to dead beetles
Oil beetles’ cantharidin, found in hemolymph, can blister skin, posing another risk to homeowners.
Life Cycle of Oil Beetles
- Oil beetles, also known as blister beetles, lay their eggs in soil
- After hatching, larvae (called triungulins) are active and search for food
For example, they may climb onto flowers to feed on pollinators like bees.
- Once they find a host, they transform into a legless, grub-like stage and feed
- After several molts in this stage, they develop into pupae
Pupae are usually found in a protective cocoon.
- Adult oil beetles emerge from pupae after metamorphosis
- Males and females search for mates to reproduce
Characteristics of Oil Beetles
- Soft bodies
- Elongated, narrow, and cylindrical shape
- Range of colors, including black, gray, and striped patterns
|Usually smaller than females
|Often larger than males
|Mature earlier in life cycle
|Take more time to mature
|Focus on finding and attracting a mate
|Lay eggs in soil for next generation
Oil Beetles Life Cycle
- Eggs laid in soil by female beetles
- Larvae (triungulins) hatch and search for food
- Legless, grub-like stage occurs after finding a host
- Pupal stage inside a protective cocoon
- Adult beetles emerge and search for mates
- Mating occurs, and life cycle begins anew
Natural Predators and Defense Mechanisms
Common Enemies of Oil Beetles
Oil beetles face a variety of natural predators, some of which include:
- Birds: Various bird species feed on beetles.
- Ladybugs: Surprisingly, some ladybug species consume other beetles, oil beetles included.
- Other insect predators: Certain insects may prey on oil beetles during their vulnerable larval stage.
Despite these potential threats, oil beetles possess multiple defense mechanisms to protect themselves.
How Oil Beetles Protect Themselves
- Physical adaptations: Oil beetles have a hard, armored body, with a sturdy head and six sharp legs, making it difficult for predators to attack them.
- Chemical defense: Interestingly, when threatened, oil beetles can secrete a highly irritant substance called cantharidin from their leg joints as a defensive measure.
|Tick legs and secreted cantharidin
|Armored body and chemical defense
These protection methods help oil beetles survive in a predatory world and make them less desirable as prey.
Control and Prevention Methods
Using chemical insecticides, such as permethrin and carbaryl, can help eliminate oil beetles from your property. These pesticides can be applied around your home’s perimeter, targeting areas where beetles are active.
- Effective in killing oil beetles
- Widely available
- Can harm non-target organisms
- Potential health risks for humans and pets
Natural Insecticides and Repellents
Neem oil is an example of a natural insecticide that is effective against oil beetles. This organic solution can be sprayed on affected areas to help control these pests.
- Environmentally friendly
- Less harmful to beneficial insects
- May require frequent application
- Can be less effective than chemical treatments
Another natural option is to use diatomaceous earth, a powder that dehydrates and kills oil beetles upon contact.
Environmental and Mechanical Controls
Implementing environmental and mechanical controls can also help manage oil beetle populations.
Physical barriers: Close up potential entry points by sealing gaps around windows, doors, and the foundation with caulk. Ensure vents are covered with mesh screens to keep beetles out.
Traps: Homemade or store-bought beetle traps can be placed in strategic locations around your property to help capture and remove these pests.
Features of effective beetle traps:
- Easy to set up and maintain
- Attractive to oil beetles
|Ease of Use
|Natural Insecticides and Repellents
|Environmental and Mechanical Controls
Remember to wear gloves and follow the manufacturer’s instructions for any type of treatment to protect yourself and others. If the infestation is extensive, it might be necessary to consult with pest control services for professional assistance.
Safe Practices for Protecting Plants and Pollinators
Preserving Beneficial Insects in Your Garden
It’s essential to distinguish between harmful and helpful insects. For example, lady beetles prey on plant pests like aphids, while leaf beetles, scarab beetles, and click beetles can cause damage to your plants.
Attracting and preserving beneficial insects such as lady beetles and pollinators like bees can create a healthier ecosystem. One method includes planting flowers that provide food and shelter for these insects.
Examples of Beneficial Insects Attracting Plants
Choosing Eco-Friendly Insecticides
Using eco-friendly insecticides helps protect beneficial insects, pollinators, and overall ecosystem health. Here are some critical factors to consider:
- Non-toxic: Avoid chemical insecticides that can harm bees and other pollinators.
- Target specificity: Select an insecticide that only targets the harmful insects, such as grubs or leaf beetles, without affecting beneficial insects.
- Mode of action: Ensure the insecticide works via physical or biological means instead of chemically, to reduce environmental impact.
Insecticide Comparison Table
-Controls various pests
|-May require frequent applications
|-Needs reapplication after rain
|-Targets specific pests
– Low risk to beneficial insects
|-Toxic to bees when wet
-Not suitable during pollinator active hours
By following these practices, you can safely protect your plants from pests like oil beetles while preserving beneficial insects and pollinators, ensuring a healthy garden ecosystem.
Alternative Home Remedies
Natural Sprays and Solutions
One way to deter oil beetles, like those from the family Meloidae, is creating natural sprays and solutions from household items.
- For example, a mix of water and dish soap can be sprayed onto affected garden plants to keep beetles away.
- Pros: Easy to make, environmentally friendly
- Cons: May need frequent reapplication
Using Plants and Oils for Repellent
Certain plants and essential oils, like lavender and peppermint, are known to repel various beetles. Planting these in your garden can help deter beetles from reaching your roses, corn, fruits, and other garden plants.
Lavender: Effective against June bugs and other beetles
- Pros: Beautiful, fragrant addition to the garden
- Cons: May require specific growing conditions
Peppermint: Attractive to humans but repulsive to beetles
- Pros: Easy to grow, adaptable to different environments
- Cons: Can spread aggressively and become a weed
Using essential oils like peppermint oil can also prevent beetle infestations. Apply them to plants or create a spray diluted with water to cover larger areas of your garden.
|Fragrant, adds beauty to garden
|Specific growing conditions
|Easy to grow, adaptable to environments
|Can become invasive like weeds
In summary, alternative home remedies to get rid of oil beetles include natural sprays, solutions, and using certain plants and essential oils for repellent. Before applying any product or planting a new variety in your garden, be sure to research and consider the specific needs of your garden plants as well as the potential side effects of these remedies.
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 – Red Striped Oil Beetle from Spain
Is this an ant queen?
Location: Mérida, Spain
April 30, 2011 11:47 am
My daughter took a photo of this beastie when on a school trip. What is it? an ant queen? seems unlikely as they did not find it with other ants or in a nest. it doesn’t seem to have wings. What is it?
This beauty is not an ant, but a beetle, a Red Striped Oil Beetle, Berberomeloe majalis, one of the Blister Beetles. We have several contributions from Spain, including this one.
Thanks!, she will now be able to greatly impress the teacher Monday morning!
Letter 2 – Endangered Oil Beetle from the UK
Subject: looks like devils coach horse
May 19, 2015 6:42 am
a friend found this bug in west somerset England. we think it looks like a devils coach horse but bigger about 30mm long. can you help
At first we thought this was going to be a routine identification of an Oil Beetle in the genus Meloe, and the only item of significance is that all of our many reports are from North America and we did not realize that the genus was represented in Europe. As we commenced research, we were led to BugLife where we learned: “Oil beetles are incredible insects, but they are also under threat. Three of UK’s native oil beetles are now extinct, and the remaining five species have suffered drastic declines in their distributions due to changes in the way our countryside is managed. … Oil beetles have been identified as priorities for conservation action through the UK Biodiversity Action Plan (UKBAP) – meaning work needs to be done to conserve them and their habitats. To help landowners and managers our oil beetle management sheet is now available. ” Another page on BugLife provides this information: “Oil beetles are conspicuous, charismatic insects which are often encountered when out walking and enjoying the countryside. Their habit of seeking out bare compacted earth in which to dig nest burrows means that they are frequently seen on footpaths. The best time of year to look for oil beetles is March to June.
Please keep a look out for these beetles when walking in meadows, grasslands and open woodlands and let us know if you find them by submitting your sighting records and uploading your photos. Your records can make a real difference to our oil beetle conservation work.” We would urge you to be a citizen scientist and submit your sighting. Since neither BugLife page included images of Oil Beetles, we are also linking to this BBC Earth News page where it states: “Conservationists are asking the public to take part in the first survey of the UK’s threatened oil beetles. These large, lustrous insects thrive in wildflower-rich grasslands and heaths – areas of habitat that are being lost. In the last hundred years, half of the country’s eight native species of oil beetle have disappeared.” We are featuring your submission.
Letter 3 – Red Striped Oil Beetles from Portugal
Subject: Beetles in Portugal
Location: Serra da Mamede, Portugal
June 29, 2014 12:39 am
We came across these very striking beetles in dry grassland in eastern Portugal. There were several pairs, apparently biting each other’s tails. They are about two inches long with big black and red abdomens. Please can you tell me what they are?
Signature: Peter Burrows
You are astute to recognize these Red Striped Oil Beetles, Berberomeloe majalis, as beetles, as they are not characteristically beetle-like in appearance. We have several images of this species of Blister Beetle in our archives from Spain as well as Portugal. We are curious about the behavior they are exhibiting, which you liken to “tail biting” and we can’t help but to wonder if this is some type of courtship behavior.
Thank you very much for the identification.
Letter 4 – Oil Beetles mashed in the heat of passion
2 Shiny Black Bugs (Pic included)
Before you view the picture…I have to apologize. I fear I did not see them till it was too late. On top of that…it looks like they were enjoying one of the finer things in life right before I took it. I am really sorry. But I’m still curios as to what they are. I’m 25, and have lived in Pennsauken all my life, but never seen anything like them.
They have what seem to be wings (or maybey they’re just the shell covering the real wings)…a shiny black carapace with a hint of turquois. Their Antennae are segmented. (I know there is a significant difference between Segmented and smooth antenna…but I forgot what) I didn’t get a frontal shot… But their mouth-parts didn’t have any substantial mandibles. The mouth-parts resembled that of a common grasshopper…for lack of appropriate term. This picture was taken in Pennsauken, New Jersey…about a 20 min drive from Philadelphia, PA. Again, I apologize for their demise. It was not intentional. Hope you can shed a little light on it.
Thanks in advance,
You have an awesome photo of a pair of Oil Beetles who met a tragic end while procreating. Another common name is Short Winged Blister Beetle, Meloe angusticollis. The beetle is found in Southern Canada and the Northern United States. It is usually found in crop fields and meadows where it eats herbaceous foliage being particularly fond of potatoes. If disturbed, the beetle feigns death by falling on its side. The leg joints exude droplets of liquid that cause blisters.
Letter 5 – Oil Beetles Mating
Pictures of devils coach horses that are vegetarian? From wisconsin and question.
I would like to share these pictures with you. I think they are of devils coach horses, but I am not positive. I would like to know if I am mistaken on the identity. There seems to be a little discrepancy in the descriptions I have found online as to behavior and appearance. I am wondering if its a closely related, perhaps vegetarian species? The females are 1 1/4 inch long and thick bodied. Males are 3/4 inch and also thick bodied. They don’t seem to be able to move their tail ends upward since they are plump. There mandibles are small for the head size as the pictures show. They are also black with a blue green iridescence. They are calm and peaceful. And they are active in bright light. First of all, I found hundreds of these fascinating insects in a mowed field that was located in a wooded clearing out in farm country. It was mid afternoon when I found them on a warm, 80 degree, sunny, October day. I am in Wisconsin! I have lived out here, in the country, for 15 years and never before seen these creatures in our area. I brought about a dozen home to identify and observe them. They mate freely with each other, the males just go from female to female. They have been eating grass in large amounts and enjoy rye bread and adore fresh soft fruits. They ignore hard dry grains. They have a preference for the softest of plant foods.They ignore slugs. Moths that my son caught, a few squished, (he is 5 yrs old) didn’t arouse the insects interest. They have showed no desire to borrow in anything be it soil or leaf litter. They remain on top of their substrate and are most active at mid day. They don’t show any defense posture what so ever. In fact they seem quite content to munch and walk around no matter what activity is around them. In the wild, they didn’t show any defense posture when I collected them either. I would like to ask you if you could share information about these wonderfully beautiful creatures. I cant find info on their life cycle. They are mating, and I don’t know what they lay their eggs in nor the time line for hatch and etc…. I home school my daughter and this adventure with these creatures has lead us on lessons in insect discovery. The pictures show detail of the sexual difference in the antenna. I was surprised to note the difference. There is a nice view of the females back that showed the detail of texture. Also, the size difference between male and female is obvious. I liked the way the grass eating picture turned out. That (eating) seems to be their main activity, next to making droppings. Please feel free to use any pictures on your site if you choose.
My partner, Kevin Stone took the pictures of my wonderful, insect find. What is puzzling me at this point, is when and in what will they lay eggs? I also have not figured out if they are meant to live through the coming winter or will die after egg laying, and if being in a aquarium, indoors, will change their life cycle. Any info you can share would be very welcomed.
Thank you for your time,
Why are you home schooling. You should be teaching 30 children. Your letter is absolutely awesome. These are not Devil’s Coach Horses, but Oil Beetles, a type of Blister Beetle, Meloe angusticollis. The adults eat grasses as you know and are fond of the foliage from potatoes. Larvae are parasitic on wild bees, and unless there is a wild bee nest in your aquarium, you may not get eggs. Be careful in handling the beetles which can exude droplets from their leg joints that might cause blisters.
Letter 6 – Oil Beetle from Hungary
I’m Laszlo Nemeti from Hungary. I ask what’s that bug? This is 4-5 cm long bug, shining dark blue color. Thank you!
This is a Blister Beetle in the genus Meloe. In the U.S. they are known as Oil Beetles, probably because of their oily irridescent appearance.
Letter 7 – Oil Beetle: Exterminated ???
my boss [runs a tree-trimming, spraying etc company] found a bug … i’ve attached a photo – not the best photo = i took it. do you think it is an “oil beetle”? we are located in stockton new jersey, but do tree work in new jersey and pennsylvania, so is it possible that oil beetles are in our area?
thanks for your help?
Yes, this is an Oil Beetle. They are also known as Short Winged Blister Beetles and are in the genus Meloe. They are found in your area. According to the Audubon Guide: “If disturbed, this beetle feigns death by falling on its side. Leg joints exude droplets of liquid that cause blisters.” We are hoping your photo shows this feigning death behavior and is not the result of extermination.
Letter 8 – Oil Beetles
Found these beautiful blue bugs in between some wild clematis and swamp milkweed. I have never seen them before. They were about an inch long, maybe an inch and a half. They were found mid-day in Great Barrington, Massachusetts. Thank you so much!
These are Short Winged Blister Beetles, commonly called Oil Beetles.
Letter 9 – Oil Beetles
what is this bug
Location: Southwest Virginia
October 27, 2011 3:50 pm
Every fall I see these things in my backyard. They gather together on a certain plant and I guess they eat it. Anyway it always dies where they were.
These are Oil Beetles, a group of Blister Beetles in the genus Meloe. There are 12 similar looking species on BugGuide, and we don’t have the necessary skills to differentiate your species from the others. Because of your location and the time of year, we believe the most likely species candidates based on data information on BugGuide are Meloe campanicollis and Meloe impressus. Oil Beetles have an interesting and complex life cycle that includes laying eggs that hatch into mobile larvae that attach themselves to solitary bees. When the bee returns to the hive, the beetle enters with the bee and begins by feeding upon the egg of a bee as well as the food that has been provided to nourish the bee larva. Here is the explanation on BugGuide: “First-instar larvae climb to the top of a grass or weed stalk as a group, clump together in the shape of a female solitary ground bee, exude a scent that is the same as, or closely resembles, the pheromones of the female bee, and wait for a male ground bee to come along. When he does, he tries to mate with the clump of larvae, whereupon they individually clamp onto his hairs. He then flies away, finds and mates with one or several real female bees, and the larvae transfer to the female(s). Each impregnated female bee then flies off and builds one to several nests in burrows she digs in the soil, and the larvae transfer again to the new nests. The female bee stocks these nests with honey and pollen for her own young, but the hungry blister beetle young are there to gobble up the provisions. They eventually pupate and finally emerge as adult flightless beetles. Brothers and sisters find each other and mate, produce eggs and the hatchlings start the process all over.” BugGuide does not provide much information on the food plants for the various species. Have you been able to identify the plant that your beetles are feeding upon? Is it something that you cultivate in your garden or is it a native plant? The Backyard Arthropod Project has a nice set of photos and some interesting observations.
Letter 10 – Possibly Oil Beetle emerging after metamorphosis
Some Sort of Half-Buried Beetle?
Location: Southwestern Virginia (Mouth of Wilson)
March 20, 2012 8:58 am
As I was walked to work this morning I saw this funny little fellow sticking up out of the ground. I positively adore bugs so I ran to work, borrowed a camera, and snapped a few quick shots. What is he? Why is he sticking out of the dirt like that? Is he crawling out for spring? Anyway, thanks Bugman, I’m a huge fan but this is the first time I’ve found an insect that’s stumped me enough to ask about it.
This are pretty amazing photos, and we are going to speculate on what we believe they might document. This appears to be an Oil Beetle, a species of Blister Beetle in the genus Meloe. Oil Beetles should be handled with caution, or even better, not handled at all. Blister Beetles are known to exude cantharidin, a compound that causes blistering in human skin. We suspect this Blister Beetle which appears to be a female without notches on her antennae (See BugGuide). We know nothing about Blister Beetles digging into the earth, but they might emerge out of it. Oil Beetles are also called Short Winged Blister Beetles.
Update: March 31, 2012
We just discovered this wonderful information on the Encyclopedia Britannica Online website that supports our theory that this is an Oil Beetle emerging after metamorphosis. Here is the information: “blister beetle (family Meloidae), any of approximately 2,500 species of beetles (insect order Coleoptera) that secrete an irritating substance, cantharidin, which is collected mainly from Mylabris and the European species Lytta vesicatoria, commonly called Spanish fly. Cantharidin is used medically as a topical skin irritant to remove warts. In the past, when inducing blisters was a common remedy for many ailments, cantharidin was commonly used for this purpose. It was also a major ingredient in so-called love potions. Blister beetles are both helpful and harmful to humans. The larvae eat grasshopper eggs, and, if abundant, adults can destroy crops.
Adult blister beetles are often brightly coloured, the need for camouflage being eliminated by their ability to secrete cantharidin. They range between 3 and 20 mm (0.1 to 0.8 inch) in length, with the majority between 10 and 15 mm (0.4 and 0.6 inch). Their long, slender, leathery bodies are covered by metallic green or blue wing covers, often marked with bands or stripes.
The female lays between 3,000 and 4,000 eggs; only a few of the young survive, however, because of their complicated and haphazard life history (hypermetamorphosis). The female of Sitaris muralis deposits masses of eggs near solitary bees’ nests. The larvae hatch from the eggs and remain dormant throughout the winter. In the spring tiny active forms (triungulins), sometimes known as bee lice, attach themselves to a bee. They feed on eggs and stored food in the bee nest as they pass through several more developmental stages, changing from a larva to a legless grub. When the pupal stage is complete, the newly emerged adult drops to the ground and begins feeding on cultivated plants.
The female of some blister beetles (e.g., Epicauta vittata) deposits masses of eggs either on or in the ground. The triungulin feeds on grasshopper eggs, undergoes a series of molts (periodic shedding of skin), and spends the winter in a pupallike stage. After passing through several more larval stages and a true pupal stage, the adult blister beetle emerges.
The members of the subfamily Meloinae are sometimes known as oil beetles. They do not have hindwings as do most blister beetles, nor do their wing covers meet in the middle of the back; rather, the covers are much shorter and overlap. Oil beetles secrete an oily substance that protects them from predators because of its bad taste. In some species the forcepslike antennae of the male are used to hold the female during mating. An oil beetle genus common in both Europe and North America is Meloe.”
Letter 11 – Oil Beetles leave tracks in the sand
Beetle at the beach
Location: Brigantine Beach, NJ
April 10, 2012 8:01 pm
Hello – These beautiful black beauties were discovered on one of the paths that lead through the dunes toward Brigantine Beach in New Jersey. I first noticed the awesome ’footprints’ then spotted half a dozen of these ’beetles’ (at last an inch-long and males slightly smaller than females) mating and simultaneously chomping on the first greens of the early spring March 24th, 2012.
Signature: Naturelady Christina
Dear Naturelady Christina,
These are positively marvelous photos of Oil Beetles in the genus Meloe. The lighting really accentuates the tracks in the sand. Oil Beetles are Blister Beetles that should be handled with caution as they exude a compound known as cantharidin that can cause blistering in skin.
According to BugGuide, the individuals with the notched antennae are the males and they are generally smaller than the females.
Letter 12 – Oil Beetles
Subject: Beetle ID please
Location: TwinLakes, WI, USA
October 18, 2012 11:52 pm
Hi-Found two amazing critters: one 40mm, the other 30mm long. They were in a recently aerated lawn area a few yards apart from each other. 50* temps, good rainy days, shady part of property, TwinLakes, WI, USA. I’ve been digging in the dirt for 30+ years and have never seen this sort of insect. Smaller one gets on the back of the larger one…alot. Male/female? How to tell them apart other than size? or not. Thanks for your time –
These are Oil Beetles in the genus Meloe, and there may be as many as 22 species in North America according to BugGuide. Also according to BugGuide: “Males smaller than females, with modified antennae.” We cannot discern the smaller individual’s antennae in your photo because the slow shutter speed resulted in a blur. Are the two solo shots photos of the larger or smaller individual, because that individual is a female. We wonder if this is a viable pair or a same sex couple.
Letter 13 – Oil Beetle makes off with Quarter
Subject: What’s that??
Location: Drexel Hill, PA
November 2, 2012 1:41 pm
This is the second time I’ve seen this bug on my lawn. It has no wings & seems to be eating grass. They are a very darkhappy green (almost black) color. This morning I had about 5 of them within about 2 feet of eachother outside. Some of them seemed to be mating. I’ve never seen them before in my life so I’m curious as to what they are.
We can’t for the life of us figure out what that Oil Beetle in the genus Meloe wants with that quarter. We do have another image in our archive of a pair of Oil Beetles trying to abscond with a dime.
Letter 14 – Oil Beetle secretes Cantharidin
November 14, 2012 1:14 am
Could you please tell me what this is, I thought it was a beetle. But, on closer exam no wings and its soft.
This is an Oil Beetle, one of the Blister Beetles in the genus Meloe. Oil Beetles and other Blister Beetles are capable of secreting an oily substance from their joints that contains the compound Cantharidin which can cause blistering in human skin, so they should be handled with caution. Your individual is secreting oil in a droplet from the middle leg on the right side of the photo.
Thank you so much for responding. I’m glad I didn’t touch it now.
Letter 15 – Oil Beetles
Subject: What kind of Insect is this?
Location: East Hampton, NY
November 18, 2012 7:20 pm
Took this in the garden in East Hampton, NY on Nov. 17, 2012. We have a big vegetable garden, and while harvesting some fall crops we encountered many of these. They were near the escarole. Never seen them before in 25 years of gardening. When you touch them it seemed like they would lay down and play dead. Also appeared as idvthey were mating. Very interested in knowing what they are…
Signature: Edward Del Gado
These are Oil Beetles, a type of Blister Beetle in the genus Meloe. Blister Beetles should be handled with caution as they produce a compound cantharidin that can cause blistering in human skin. Your submission will go live in the next week as we are preparing postings on a daily basis in anticipation of the Thanksgiving holiday.
Daniel… Thnaks so much for the response. Why did they suddenly appear? Do they come from underground?
Hi again Edward,
BugGuide has this nice description of the life cycle: “First-instar larvae climb to the top of a grass or weed stalk as a group, clump together in the shape of a female solitary ground bee, exude a scent that is the same as, or closely resembles, the pheromones of the female bee, and wait for a male ground bee to come along. When he does, he tries to mate with the clump of larvae, whereupon they individually clamp onto his hairs. He then flies away, finds and mates with one or several real female bees, and the larvae transfer to the female(s). Each impregnated female bee then flies off and builds one to several nests in burrows she digs in the soil, and the larvae transfer again to the new nests. The female bee stocks these nests with honey and pollen for her own young, but the hungry blister beetle young are there to gobble up the provisions. They eventually pupate and finally emerge as adult flightless beetles. Brothers and sisters find each other and mate, produce eggs and the hatchlings start the process all over.” Pupation is underground, so adults will emerge from underground when they complete metamorphosis.
Letter 16 – Oil Beetles
Subject: Baffled by Big Black Bug
Location: Beaverton, OR
April 26, 2014 7:41 pm
My son and I were in a nature park today, and found many of these large insects. They were ambling through short clover and grass by the side of the trail. I’ve been trying to identify them but am completely baffled! Any help greatly appreciated!
Signature: Laura B
This is one of the Blister Beetles in the genus Meloe, and they are commonly called Oil Beetles. We are uncertain of the exact species, however, according to BugGuide, Meloe strigulosus is found along the “Pacific coast from Kodiak, AK to Baja & AZ.”
Thank you so much! The shape of its head had me thinking it was related to ants and wasps, and its unusual elytra had me thinking it could not be a beetle. I was totally on the wrong track. You are quite amazing! I definitely appreciate your hard work, which I know does much to spread the wonder of bugs.
Just in case it’s interesting, here’s another picture from the same excursion of a tiny critter we found in a pond. My “Pond Life” book leads me to believe it’s not a larva but a mosquito pupa. I had no idea that pupas could be free swimming, lively animals as opposed to motionless inside a cocoon!
Thank you again,
Letter 17 – Oil Beetle from Canada
Subject: black beauty
Location: Toronto, Ontario, Canada
October 25, 2014 7:49 pm
This black beauty was photographed today, Oct 25 in a ravine in Toronto, Ontario Canada. It was about 1-1/14″ long and moving steadily through a grassy area. We thought it looked like it was full of eggs or something since its abdomen was so huge compared to the head and thorax.
Signature: anne murphy
This distinctive insect is an Oil Beetle, a species of Blister Beetle in the genus Meloe. According to BugGuide: “Males smaller than females, with modified antennae” and several images of the modified antennae are included. Your close-up image of the Oil Beetle’s head appear to show the modified antennae, so though you suspected this to be a gravid female, we believe it is a male Oil Beetle.
Thank you so much Daniel! I am so glad you could identify that insect. Now I’ll look it up and learn more about it. So, the female would be even bigger. Wow! Hope we come across one some day. Thanks again.
Letter 18 – Oil Beetle from Canada
Subject: Odd bug in the park
Location: Southern Ontario, Canada
December 20, 2015 5:53 am
Dear bug man,
We saw this large insect while walking to school last week, and got our mother to take a picture. It was about two cm long. It was a warm day in December.
Signature: Bug-watching sisters
Dear Bug-watching Sisters
This is an Oil Beetle, a species of Blister Beetle in the genus Meloe.
Letter 19 – Oil Beetle from Hungary
Subject: Shiny blue 3-segmented in Hungary
Location: Southern Hungary
June 19, 2017 10:59 pm
I have recently moved to Hungary and am enjoying exploring and identifying some of the bug life with my children. I was unable to ID this one.
It is quite shiny, almost metallic in the sun. It appears to have 3 segments.
My initial thought was some sort of Cuckoo Wasp but it’s so large, and honestly looks more like an ant. I found 3 of them in a day. Each was alone, all in soft soil alongside a walking path in a deciduous forest. Sometime in mid April.
Letter 20 – Oil Beetles
Subject: big black bug
Geographic location of the bug: Taunton, MA
Time: 04:12 PM EDT
There was a small group of these bugs in the lawn – they seemed to be eating the leaves
How you want your letter signed: Michele Restino
Letter 21 – Oil Beetle from Canada
Subject: Large bluish beauty
Geographic location of the bug: Outside Sackville, New Brunswick, Canada.
Time: 11:38 AM EDT
Your letter to the bugman: Walking near my parents’ trailer, I nearly stepped on this rather beautiful creature and couldn’t help but wonder what it is. It was generally inclined to stay still, but once I put it down, after lifting it for closer inspection, it was happy to race over very course gravel in order to get back to the tall grass.
How you want your letter signed: Parker
This is a Blister Beetle in the genus Meloe, commonly called an Oil Beetle because the iridescent surface of the beetle looks like oil on water. Blister Beetles should be handled with caution, as many species are able to exude a compound called cantharidin that is known to cause blistering upon contact, especially in sensitive individuals. The “crook” in the antennae indicates this is a male Oil Beetle.
Blister Beetles as a family tend to have complex life cycles. Of the genus Meloe, the Oil Beetles, BugGuide states: “Larvae feed on eggs and other food in bees’ nests” and “In some species, triungulins [see definition below] aggregate and use chemical signals to attract male bees to which they attach themselves. This allows transport (and transfer) to a female bee who carries them back to her nest (Saul-Gershenz & Millar 2006). First-instar larvae climb to the top of a plant as a group, clump together in the shape of a female solitary ground bee, exude a scent imitating the female bee pheromone. When a male bee comes and tries to mate with the clump of larvae, some of these clamp onto his hairs and eventually get to female bees when he mates for real. Impregnated female bees fly off and build nests in burrows; triungulins move to the new nests and feed on honey and pollen stocked by the bee for her own young. –Jim McClarin’s comment.” Of the family, BugGuide notes: “Life cycle is hypermetamorphic. Larvae are parasitoids. Eggs are laid in batches in soil near nests of hosts, sometimes in nest of bee host, or on stems, foliage, or flowers. Larvae undergo hypermetamorphosis–first instar larvae (usually called triungulins) are active, have well-developed legs and antennae. These typically search for hosts. Later instars tend to have reduced legs and be less active, having found hosts. There is a coarctate (pseudopupal) stage, which is usually how the larvae overwinter. Life cycle may be as short as 30 days, or as long as three years. It is typically one year, corresponding to that of host.