Oil Beetle, Meloe family
Several black beetles have been brought into the Home and Garden Center for identification during the last few weeks. They usually appear on the lawn in groups of 20 or more. They are in the Meloidae family, commonly called the Blister Beetle family due to their ability to emit an oily substance from leg joints when disturbed. Another name for them is Oil Beetles. The ‘oil’ contains the chemical cantharidin that will cause a painful blister on skin.
The adult is unable to fly due to its shortened elytra, and unfunctional wings. The adults feed on grass and several leafy weeds and flowers. The larva feed on larva of insects, mainly in underground nests of the host. There are many several different species of Meloe beetles with each one preferring a different host food as prey. The larva develop in bees’ nests where they eat the bee larva and food store’s of the bees. The female of oil beetles is larger than the male , as seen in the photo above.
Oil beetles are not considered a bad thing in the garden or lawn. They cause little damage to plants and the larva can control other pest insects. Although I would not want to see these guys in or near a hive of bees if I was a beekeeper!
-Carol Quish
Uconnladybug's Blog 
October 15, 2010 at 4:34 pm
I found a group of 8 oil beetles in my garden the other day. They were eating my chives – they eat it all! I thought these were pest insects and I distroyed them all, affraid they will go after the rest of the garden plants. I did some research later to find out about their life habits. They can be pretty distructive in the garden.
October 27, 2010 at 4:01 pm
Our yard (acre +) is INFESTED with these oil beetles, how do I get rid of them!
October 27, 2010 at 9:06 pm
The oil beetles are considered beneficial, a good bug in the lawn and garden. They feed on the larva of ground dwelling bees, usually considered a nuisance insect. Don’t worry, the oil beetles will soon be digging in for the winter, literally going into the ground during the cold weather. Insect populations go up and down depending on the weather. This year’s weather patterns were very good for the oil beetle population. Next year will should be different, therefore maybe we will not see the high numbers we saw this year.
September 3, 2011 at 4:07 am
These oil beetles are destroying my tomatoes plants! So far they are NOT good! What to do?
September 5, 2011 at 12:55 am
Hello Lj,
While wearing gloves, try to knock them into a container of soapy water to kill them. Or spray them with a strong spray of water from the hose to knock them off. Typically, they should not be eating the tomato plants, and I am not sure why they found yours so inviting. Oil beetles are crawlers, not flyers so it will take them a long while to find their way back to the plants.
Carol
January 23, 2012 at 7:37 pm
They completely demolished my chives last year! I’m growing onions and garlic this year, if they interfere I’m killing them all as quickly as possible. These are not good bugs.
October 9, 2012 at 7:45 pm
I found a total of 8 Oil Beetles on the lawn on October 6th and one or two over the weekend, and one today in East Longmeadow, Mass. I was surprised to see them eating the top of grass stems off. I believe that they were all female beetles with the exception of one mated pair.
I wasn’t aware that they were destructive to lawns, although only a few blades of grass were distirbed with only 8 of them. Has anyone else withnessed this behavior before?
October 10, 2012 at 12:10 am
Hello Karen,
Adult oil beetles will feed on various plant material including grasses. The damage from their feeding is negligible to lawns.
Regards,
Carol Quish
October 12, 2012 at 7:46 pm
We found probably 15 Oil Beetles this week in Connecticut. We left them alone, but am concerned as I have two puppies who eat anything and everything that cross their paths. I understand these are poisonious, so if a dog eats one, should I be concerned? I know, I know, call the vet right?
October 12, 2012 at 7:54 pm
Hello Carolyn,
There is a good fact sheet from Colorado State University Extension System at the link below. It talks about cattle and sheep poisoning as they are foraging animals. It is not know the number of beetles that has to be eaten to cause death. The toxin contained in and released by the oil beetles is cantharidin, a highly toxic chemical that irritates the gastrointestinal and urinary tracts and may lead to death, especially in horses. And yes, call the vet if you suspect the dog is in distress and eaten an oil beetle or two.
http://www.ext.colostate.edu/pubs/insect/05524.html
Regards,
Carol Quish
UConn Home and Garden Education Center
October 10, 2013 at 9:35 pm
Help. We have two young dogs. They like to eat bugs. I am scared with a yard full of these oil beetles it will be impossible to keep my dogs from getting in contact w/ them. How can I get rid of them?
Thanks, Katie
October 14, 2013 at 4:49 pm
Hello Katie,
I suggest keeping the dogs out of the area until the beetles move into their winter hiding places. If the beetles are on your lawn, lawn insecticides with blister beetles on the label can be used against these oil beetles. Keep the dogs off of the lawn after using the insecticide.
Regards,
Carol Quish
October 16, 2014 at 1:07 pm
At my friends home I noted a lot of single and mating pairs at the bottom of a dying evergreen. She said she can hear insects crunching up in the tree. I don’t see anything about what these large adults would eat. Could they be what is causing the tree to be dying?
October 16, 2014 at 2:49 pm
Hello Elena,
As stated in the blog, “The adults feed on grass and several leafy weeds and flowers. The larva feed on larva of insects, mainly in underground nests of the host. There are many several different species of Meloe beetles with each one preferring a different host food as prey. The larva develop in bees’ nests where they eat the bee larva and food store’s of the bees.”
The adults will not be feeding on the tree nor killing your friend’s tree. Scout for other problems that would be causing decline of her tree.
Regards,
Carol Quish
October 18, 2014 at 8:56 pm
Hi, these oil beetles have decimated my rosebush leaves (I saw them) as well as the helleborus. Is there anything that can be done? I will have absolutely no foliage left. Can’t afford to wait for winter.
October 20, 2014 at 11:19 pm
I’m concerned my young dogs will eat or step on these beatles. Please advise/ confirm how to discourage these bugs naturally. We have a huge number of ground bees in the spring. My idea is to get a better soil base in the back yard. Then: hopefully the bees won’t be interested in nesting in my yard. Then I hope the oil beetles won’t be attracted to my yard. Thoughts?
October 21, 2014 at 1:15 pm
Hi Rita,
You can use an insecticide on the leaves of the plant when the oil beetles are present and feeding.
Regards,
Carol Quish
October 21, 2014 at 1:18 pm
Hi Katie,
To decrease populations of ground dwelling bees, increase organic matter in the soil by core aerating and top dressing with mature compost or other material that will increase moisture holding properties. If you see oil beetles, you can use an insecticide on the leaves of the plants they are eating.
Regards,
Carol Quish
November 13, 2015 at 8:36 pm
I Have been fighting these beetles for two years. I have sheep and horses,lost a pony to this. We have tried seven as a recommended insecticide to no avail. I hand pick each day in a three acre pasture. What insecticide would be toxic to them? The seven didn’t work. Help!!
November 13, 2015 at 8:38 pm
What insecticide works tried seven which was recommend have lost a pony to this.
April 18, 2016 at 3:06 am
They are stripping my garlic leaves ..they are not benign!
April 25, 2016 at 10:30 pm
I am in Southern Washington State (Klickitat County). The local Extension ID’d these beetles for me. I am farming garlic, and they are eating the leaves all the way down. Since I’m farming organically, I have just been checking 2x day for them and destroying them. My puppy who does like bugs and beetles would not touch these, so there’s hope for the dog owners.
Melissa, how did you lose a pony to this? The pony ate the beetles or the insecticide? How large a pony?
October 18, 2016 at 6:15 pm
I live in mich. these beetles return every year. We have a dog as well. I now have to go out to my back yard 2 daily to bucket these in antifreeze. I hate to use such a product. But, I have found that it works the best. I make sure to keep the bucket away from anyone. I use a shovel to scoop them up. I never let the dog out while doing this. Antifreeze is sweet smelling. She would eat all the beetles if I don’t watch her. How do you prevent them from coming every year. What do I need to put on the lawn before winter or before they come out??? I am tired of chasing a bucket of bug along with the daily poop scoop!!
October 18, 2016 at 7:01 pm
Hello Brandy,
Please stop using antifreeze. This an illegal and dangerous use of the product. Animals, especially dogs, are highly attracted to antifreeze and it will kill them if they drink it. It causes kidney, liver and brain damage.
There are much better and legal ways to kill insects. A bucket of water with liquid soap mixed in kills insects including oil beetles. Use laundry, dish or hand soap. Soap clogs insects’ breathing tubes suffocating them. Oil beetles are not listed as pests and are only active a few weeks of the year.
Regards,
Carol Quish
October 13, 2017 at 11:35 pm
just looked at a home in macomb twp MI and there were 1000’s of big black bugs that look like this all squirming around in the front and backyard…. the entire lawn was covered… looked like something out of a si fi movie…. freaky
Never seen a bug like that before.