Beetle
Location: East San Diego County, CA
December 13, 2011 10:54 am
We found this bug on Sunday. He was hitting the windows and the door in the evening hours. We’ve seen these kind of bugs before, but only when it rains. It was damp and raining that day and 47 degrees. We are at an elevation of 4,000 ft., near the border of Mexico and California. We found it dead on a bucket the next morning.
Signature: Mark

Rain Beetle

Dear Mark,
While this is not a rare sighting, it is a somewhat unique sighting.  Your beetle is a Rain Beetle, a member of the family Pleocomidae and the genus Pleocoma.  This is a small family that is limited to coastal regions of the west coast of North America from Washington to Baja.  This family is not known from any other parts of the world.  There is work needed on the taxonomy of the genus and it would be nearly impossible for us to provide you an exact species identification.  According to BugGuide, there are approximately 30 species identified.  Many species have very limited ranges, due in large part to the morphology of the flightless female.  One can only begin to ponder what conditions once existed that allowed the range expansion and genetic diversity that contributed to the evolution of distinct species where the female of the species is flightless and immobile.  The grubs live underground, often at great depths, feeding on the roots of oaks and conifers according to BugGuide.  You may find this May 18, 2009 Los Angeles Times article interesting.

2   I like This

Related posts:

Rain Beetle Rain Beetle Rain Beetles Rain Beetle

Found a bug
Location: Northern Ca foothills near Auburn CA
November 13, 2011 1:58 pm
Hi, I found this bug on my doorstep this morning. It is about 2 inches long. Not sure what kind it is and if I should be concerned about the trees or house. We live in a heavily wooded area, many pines and oaks in the Sierra Nevada foothills near Auburn CA.
Can you tell us what bug this is?
Signature: Duke

Rain Beetle

Hi Duke,
Congratulations on your wonderful sighting.  This is a male Rain Beetle in the family Pleocomidae (see BugGuide), a family with a range that is limited to the west coast of North America.  Rain Beetles are a very unusual family of beetles.  Larvae live underground and feed on the roots of oaks and conifers and they can remain underground for as long as ten years.  Mating activity is triggered by rain.  Only male Rain Beetles have wings, and they will circle the ground until they locate the burrows of a flightless female.  There are many species of Rain Beetles and many have very limited ranges.  An expert is required to distinguish one species from another.  There was an excellent article in the LA Times several years ago on the Rain Beetles. 

2   I like This

Related posts:

Rain Beetle Rain Beetles Rain Beetle Rain Beetles

Is this a Rain Beetle?
November 18, 2009
Just found in the pool flailing around on top of the water — it looks like the other Rain Beetle pictures on your site and thought I’d ask if that’s what this is to confirm. One picture is on top of the net I got it out of the pool with. The other is on the ground. We had rain last night and everything is still sort of wet around here today. Thanks!
Elaine
Rural Windsor, California (North of Santa Rosa)

Rain Beetle

Dear Elaine,
You are absolutely correct.  We are happy that our website was helpful with your Rain Beetle identification.  This is the second submission of Rain Beetles we are posting from yesterday.

Rain Beetle

3   I like This

Related posts:

Rain Beetles Rain Beetle Rain Beetle Rain Beetles

rain beetle photos
November 18, 2009
I came to your site to find out what these are. and now i know, thanks! Here’s the photos i was going to use, enjoy!
dr
northern ca. foothills

Rain Beetle

Hi dr,
Thanks so much for the Rain Beetle photos.  We also believe the LA Time article we read this past May is once again live on the website.  It is a wonderful account of an encounter with Rain Beetles.  One of the chapters in our book has to do with insects and weather, and we are going to be writing about the Rain Beetles of the California Sierras.  Since we only have twelve days to finish the manuscript, we may write that chapter next.

Rain Beetle

0   I like This

Related posts:

Rain Beetles Rain Beetles Another Rain Beetle Rain Beetle

Looks and acts like a “Junebug”, but comes in the Fall around here
November 12, 2009
Two people have told me these bugs, which are large, clumsy and hit the window at night, are “pine beetles” or “pine borers”, which I have a hard time believing. We do live amongst a lot of oaks, cedars, yews, spruce, etc., but these guys act and look like June bugs and will not be around long.
Rhoni Lawrence
Sierra Nevada foothills, N. California, 2400 ft.

Rain Beetle

Hi Rhoni,
These are most definitely Rain Beetles in the family Pleocomidae, an unusual group of beetles with fascinating life histories.  Only the males are able to fly, and female Rain Beetles live many feet underground.  Males emerge from the ground after a rain and fly off in search of a mate.  There are many species of Rain Beetles, but their individual ranges are quite limited, and an expert is required to distinguish one species from another.  There are some nice images on BugGuide.  We read an awesome article about Rain Beetles in the LA Times this spring, but alas, the link online indicates that there is scheduled maintenance on the site and we are uncertain when it will be available.  In lieu of not being able to link to the LA Times article, we are linking to a Bay Nature website with some information.

Rain Beetles

3   I like This

Related posts:

Rain Beetles Rain Beetles Rain Beetle Rain Beetle

Is this a scarab beetle?
Fri, Nov 28, 2008 at 8:48 AM
Dear Folks,
Could you please help me identify the beetle in the attached pictures? The closest match I could find was a scarab beetle. For the past few weeks (November) our cats have been bringing these into the house. I can’t remember ever having seen them outside in the garden and I thought I was pretty familiar with most of the larger insects we have here in southwest Oregon.
They are a little over 1 inch long with a lot of what looks like fur on their underside and legs. I am sorry the pictures are so poor; we only have one of those point and shoot cameras without any setting to take close-ups of less than 3 feet.
Your site is where I go first whenever I come upon an unknown insect. I’m immensely grateful for the work you’ve put into this. Thank you so very much.
Elizabeth Hunter
Grants Pass Oregon

Rain Beetle

Hi Elizabeth,
Until today, we would have begun our response with “Yes this is a Scarab Beetle” and then gone on to further classify it as a Rain Beetle. We have just learned, upon visiting BugGuide, that Rain Beetles are no longer considered to be in the family Scarabaeidae, but have been classified into their own family, Pleocomidae . Only male Rain Beetles can fly. The female Rain Beetle remains buried deep underground in a burrow and must wait for a male Rain Beetle to locate her so they can mate. According to BugGuide, there is a single genus, Pleocoma, in the family Pleocomidae, and the genus has 34 species that range in: “Western Coastal North America, from Southern Washington to northern Baja California, Mexico and Utah. ” The individual species of Rain Beetle often has a very limited range. Rain Beetle Grubs feed underground on the roots of oaks and conifers. We are thrilled to have your images and letter for our archives, and we will be creating a new beetle category for Rain Beetles and moving the earlier postings out of the Scarab Beetle category.

Rain Beetle

Dear Daniel,
Thank you so much for your answer; I hadn’t really expected a response as I am sure you must be besieged with questions. This made my day!
The next time one of the cats presents me with a Rain Beetle I will try to get better pictures.
Thanks again for the terrific site.
Best regards,
Elizabeth

1   I like This

Related posts:

Rain Beetle Another Rain Beetle Rain Beetle Rain Beetle

Are these rain beetles
I was cleaning my pool this morning just before preparing to close it for the winter and out of nowhere, I found a bunch of these guys floating around. AT first I thought that they were bark beetles as the pool was directly under a large Ponderosa Pine but upon a bit of internet sleuthing, and since it rained for the first time yesterday, I think perhaps these are rain beetles. Is that correct? If so,are they a benign insect or do these do damage to the tree roots? Should I be concerned about them. Please advise……….
Stuart

Hi Stuart,
What a nice collection of Rain Beetles, Pleocoma species, you have amassed. Though they feed on tree roots, they are never plentiful enough to do any damage.

0   I like This

Related posts:

Rain Beetle Rain Beetles Rain Beetle Rain Beetles

rain beetle
Thanks so your great site that my husband found-we ID’d the rain beetle! My husband was sitting on the couch reading on an early dark morning ( I had just gone outside and left the door open) and INCOMING INCOMING a giant slow-moving buzzy creature came motoring toward my husbands head! He ducked and ran in the corner waiting for it to land so I could catch it and and put it outside it as I do spiders and bugs. We thought it was an amazing bug with cool appendages. My question-are the larvae harmful to tree roots-or is it a symbiotic relationship? Also, is the guy still studying them (from your website 2004)? We heard they are common here in Paradise, CA. Here are my photos.
Dawn

Hi Dawn,
We are so excited to get your photos of this fascinating beetle. To the best of our knowledge, there is no current study. We checked with Eric Eaton and here is what he has to add: “In answer to Dawn’s question: These beetles are almost never numerous enough to do damage to trees, though it is not a symbiotic relationship (the larvae EAT the roots!). She should count herself lucky to see one. The different species seem to have very localized distributions. We had them in Oregon, but not in my local neighborhood. I also do not get up nearly early enough to see them:-) Ha! Morning people…. Just to add to the rain beetle thing. The ones you see are all males. Females are flightless and call the males to their burrow entrances with a pheromone. Females are substantially bulkier than males, too. Eric”

1   I like This

Related posts:

Rain Beetle Rain Beetle Another Rain Beetle Rain Beetle