Pleocoma tularensis

Well it finally happened. After three years of searching, I finally found a rain beetle. I’m guessing that it is Pleocoma tularensis, but with the superficial (shall we say “stormy”) nature of rain beetle taxonomy, it might end up being P. fimbriata. In A.C. Davis’s revision, the two species are very difficult to distinguish. Linsley’s key to species resorts to geography to tell them apart. To complicate things, I found this individual in Fresno County fairly close to the point where the distributions of the two species meet. When this group is better understood, I expect that P. tularensis will be a subspecies of P. fimbriata (as Davis originally proposed). For those of you new to rain beetles, they are fairly large scarab-like beetles (family Pleocomidae at the moment). This one is well over an inch (30 mm) long.

Rain has come quite late this season. We normally have a good storm in November (maybe earlier). And it is this first storm that brings out the beetles (at least in many of the species). The first storm this season came this last weekend (in the middle of January). It starting on Friday afternoon and so I hurried home from work the same day, grabbed a bite to eat and drove up to Bretz Mill Campground about an hour above Fresno. I chose the place because the area combines grassy areas with mixed forest and riparian habitats. And it is also between 3,000 and 4,000 feet – a good elevation for rain beetles.

I put up two lights in the rain and waited a couple of hours without success. Maybe I should have left the lights on longer. Not wanting the rain to ruin my lights, I put them away and crawled into the back of the truck to sleep. By 6:00 the next morning I was wide awake and decided to drive home. Fortunately, I passed by a small community along the way with lights on and stopped to see what I might find. I found this individual crawling along the ground below one of the lights. (Both pictures are staged.) It was 6:40 AM, not much above freezing, with small patches of snow about, and with not another insect in sight. What a great way to catch beetles – and such an impressive one at that.