Rainbeetle season

Though I typically go out and about looking for ground beetles, occasionally I abandon any thought of self-esteem and chase scarabaeoids, longhorn beetles and such. In California, the autumn and early winter rains bring out both Pleocoma rainbeetles and me to chase them.  The folks on the Berkeley side of the hills get Pleocoma behrensi, but out my way in Concord I get Pleocoma hirticollis, apparently Pleocoma hirticollis vandykei, if you are into subspecies.

Pleocoma hirticollius male, Contra Costa Co.

Unlike many of the other species in the genus,  P. hirticollis is a grass root feeder and so far, I have never seen a male fly to a light. However, sometimes they do seem dazed by my headlamp. The population near me seems small or at least few males fly at once. I saw only seven males my last time out. Other species, in other places in California (people tell me anyway) one can see 50-100 males at lights in one night.

To get the beetles I head out before dawn, and make sure I get to the site about 45 minutes or an hour before sunrise. I don’t bother going out unless the local tip-gage shows about one inch of rain the last 24 hours. It doesn’t have to be raining, but it doesn’t hurt. During my walk sometimes I encounter skunks, coyotes, turkeys and deer. They all seem a little put off that a human is invading their early morning routine. Luckily the skunks aren’t too put off. What could be crazier than jumping out of snug bed, way before dawn, and walking around in the cold rain?

But I do it and I did get beetles again this year. Found them after the first rain, just this week past.  I took one male this time, just for the record. I have enough males of this species, but have not yet found the females. I am told that the female’s burrow is very hard to find for this species.  As grass-feeders, it is well camouflaged in thick and often matted grass. I have tried following males, but so far no luck at all. They haven’t led me anywhere but around in circles. I am waiting for the next rain.

Pleocoma hirticollis vandykei grassy hillside habitat on a wonderfully gloomy morning

Is there any better thrill than seeing the flash of beetle as it flies through the mist-filled track of your headlamp light?  That thrill is fleeting though, the beetle dips, zags and wheels off into the dark, leaving only the vapor from my now rapid breath to fill my headlamp beam. I’m sure I will be able to follow the next one.

*Special thanks to the Save Mount Diablo group for allowing me access to their properties.


About Kip Will

I'm an insect systematist with expertise in carabid beetles, who is always happiest in the bush.
This entry was posted in Coleoptera, Entomology and tagged , . Bookmark the permalink.

7 Responses to Rainbeetle season

  1. Always a treat to find another beetle-centric blog.

    I hope someday I get the chance to look for rain beetles.

  2. Bugman Dan says:

    How many beetles did you see? Do they disappear at sun-up, even if it’s cloudy?

    • Kip Will says:

      The first day out only seven. Yesterday on three, but we didn’t get that much rain. I have only ever seen them within 45 minutes after sunset and from about 45 minute before sunrise. Five or ten minutes before sunrise they vanish, even when cloudy. I haven’t been out on a day when it is still raining after sunrise, so it may be cloudy, but still pretty bright. I am hoping for a good rain of an inch or more soon. That should get ’em moving.

  3. Bobby White says:

    Thanks so much for bringing him to class last week. What are we going to get to see tomorrow?

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