Currently viewing the category: "Rain Beetles"
What's That Bug? does not endorse extermination

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

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

Rain Beetles

What's That Bug? does not endorse extermination

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

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

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

What's That Bug? does not endorse extermination

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.

What's That Bug? does not endorse extermination

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”

What's That Bug? does not endorse extermination

Giant beetle creature! Whazzit??
Hi there. Your site is really fantastic! While flyfishing the other day (northern California area), I came across several of these HUGE beetles. Some were swimming (rather pathetically). They have wings of a sort but it seemed to never occur to them to fly. Any clue on its ID? Thanks much!
Michelle Mahood

Hi Michelle,
You have a photo of a Rain Beetle, Pleocoma species, one of the Scarab Beetle Family. According to our favorite expert Hogue: “The first measurable late fall or winter rains stimulate the adult males of this genus to emerge from their subterranean burrows, in which they have lain as pupae for more than a month. In some species a soaking rain of several inches is needed to initiate activity, but the species found at higher elevations will often fly a few minutes after the onset of the year’s first shower. In the foothill and canyon areas, the males seem to emerge in response to the rain and may be attracted to light, congregating around store fronts or dwellings during a drizzle or downpour. When searching for the burrows of the flightless female beetles, the males fly in slow sweeping patterns low over the ground and brush. … The females are seldom found outside their burrows, which may extend from 4 to 6 feet into the soil. The male apparently locates the burrow of the female by detecting a strong [musky] scent that she puts into the air. He enters her burrow to copulate, after which the female plugs the burrow’s opening with pulverized soil and digs deep in the ground. The eggs, which are laid in a spiral at the base of the burrow and packed tightly in fine soil, do not mature until the following spring or early summer. … The life cycle may last as long as ten or twelve years, with the larvae feeding on the roots of varied kinds of plants, usually hardwood shrubs or trees and in particular oaks and conifers. The mouthparts of the adults are atrophied and useless for feeding.” Your beetles were not swimming, but probably just bumbled into the stream. Thanks for a new addition to our site.

Ed. Note: We received this letter shortly after posting the Rain Beetle photo.
Rain Beetles Hello: I am a biologist studying rain beetles in California, and came across the posting of the rain beetle on your website. I would be very interested in finding out the exact locality where the beetle was seen. Would it be possible for you to contact the woman who posted the picture and question and either give her my email to contact? Thanks! -Ian
We forwarded Ian’s letter to Michelle who wrote back to us:
Thanks for passing my email along. I heard from Ian last night and sent him some whopping big high-res photos of the rain beetle — even the underside. How cool that someone is studying them! Thanks again for ID’ing my bug. You guys are EXTREMELY COOL. Best regards, Michelle

Ed. Note: We just got this letter.
(08/09/2005) identifications Hello – I was recently shown your site, and it is excellent. My specialization is longhorned beetles, and in cruising around I notice a number of incomplete or uncertain IDs for this family. I don’t know if you are interested in receiving this sort of input, but if you are, I offer the following additions to your identifications.
The Northern California Pleocoma species sent by Michelle Mahood is undescribed, having been incorrectly recorded in older literature as P. simi, which is found in southern Oregon, and closely resembles Michelle’s beetle. The species shown in the photo occurs around the Lake Shasta basin, most often in Douglas Fir and Incense cedar forest. I will be described in my upcoming revision of the genus Pleocoma.
Keep up the good work. You are a valuable resource.
Cheers Frank Hovore

What's That Bug? does not endorse extermination