Rain Rewards Hikers with Rarely Seen Insect on Black Friday

Rainbow in overlooking Mayhew Canyon and Indian Truck Trail
Rainbow in overlooking Mayhew Canyon and Indian Truck Trail
Joel Robinson

On Black Friday, I led a glorious excursion to Santiago Peak.  At roughly 5687 feet, it is the highest point in the Santa Ana Mountains.  The 4 of us, still puffy-eyed and bloated from the excesses of Thanksgiving, met at the Rose Canyon Cantina parking lot at 7AM.  Oliver, Mark, and I loaded into Kurt's high-clearance vehicle and drove up Trabuco Creek Road (a rough dirt road with multiple creek crossings) to the Holy Jim trailhead.  It was a cold and drizzly day -- perfect weather for a 16-mile hike with 4000 feet of elevation gain.  Such a journey, would take about 9 hours with frequent stops to catch our breath and appreciate the scenic splendor. 

 After paralleling Holy Jim Creek for about a mile, we left the riparian woodland and popped into the chaparral.

Fall Foliage of Maples in Canyon Live Oak Woodland, Bear Springs
Fall Foliage of Maples in Canyon Live Oak Woodland, Bear Springs
Joel Robinson

Eventually, we found ourselves in a cavernous "canyon live oak" woodland interspersed with big-cone Douglas-firs, bigleaf maples, bay laurels, and sword ferns.

Sword Fern, Bear Springs, Santa Ana Mountains
Sword Fern, Bear Springs, Santa Ana Mountains
Joel Robinson
Female Rain Beetle, Bear Springs, Santa Ana 
Female Rain Beetle, Bear Springs, Santa Ana 
Female Rain Beetle - Underside
Joel Robinson

I noticed a hefty one with a perfect split down the middle, but it seemed to creep slowly across the path as I approached.

Female Rain Beetle on Hand, Bear Springs, Santa Ana Mountains
Female Rain Beetle on Hand, Bear Springs, Santa Ana Mountains
Joel Robinson

This had to be the biggest beetle I had ever seen in Southern California.

Manzanita, Holy Jim Trail, Santa Ana Mountains
Manzanita, Holy Jim Trail, Santa Ana Mountains
Joel Robinson

We left Bear Springs after our short lunch break and made the challenging trek to the peak.  Along the way, we enjoyed the "sweet tart" taste of ripe manzanita berries.  We froze our butts off at the top and then headed back down before nightfall.  No other beetles were observed that day.  We parted ways with the beetles fresh in our minds.  Using photos from our trip as a reference, Kurt and I investigated the beetles and arrived at the same conclusion.  It turned out that our hike coincided with a rarely seen emergence of rain beetles (Pleocoma sp.).

 

Excerpts of rain beetle life history from "Wayne's Word - Beetles" (http://waynesword.palomar.edu/ww0502.htm):

 

"...appear with the first soaking rain during late fall in coastal San Diego County and adjacent Baja California. They belong to the genus Pleocoma and are commonly referred to as rain beetles. The name Pleocoma is derived from two Greek roots, "pleos" (full or abundant) and "kome" (hair). The name translates into "very hairy," which describes these beetles perfectly, particularly their underside. Rain beetles are typically found in coastal foothills and canyons of chaparral and coastal sage scrub. After a soaking rain (usually one or more inches), male beetles make a sudden appearance at dusk, early morning, or on cloudy, drizzly days. The males fly in slow sweeping arcs throughout the foothills, keeping close to the ground in search of the larger, flightless females.

The larger, more rotund, flightless female rain beetle rarely leaves her burrow in the ground. She emits a pheromone that is apparently irresistible to the male, as she waits for him at the surface of her burrow. After mating, the female closes the entrance and lays eggs at the base of her burrow.  Both sexes of Pleocoma lack functional mouthparts and digestive tracts, and consequently do not feed during their brief adult life. With her powerful legs and clypeus, the female pushes and scoops the soil like a miniature bulldozer. Her eggs do not mature until the following spring or early summer.

Rain beetle larvae hatch from eggs deep in their mother's subterranean burrow. They are slow to develop, and have a life cycle lasting ten years or more..."


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