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Dryopidae? - Postelichus

Dryopidae? - Postelichus
Webb Canyon, ~2000 ft. elevation, Los Angeles County, California, USA
September 29, 2009
Size: ~6 mm
I rescued this wonderful beetle from the landlord's pool. After looking around, I feel fairly certain that this is a dryopid (Long-toed Water Beetle), but the family would be a new one for me and I would appreciate confirmation from more experienced coleopterists. The only other CA specimen currently in the guide for me to compare with is this fantastic series by Joyce Gross showing a Postelichus species. It looks pretty similar to mine, but I'm not familiar enough with this group to know how to rule out other genera...

Photographed on an oak leaf where I was letting it dry off. Surrounding habitat is chaparral and mixed oak woodland. There is a nearby seasonal creek, but it was dry at the time.

Images of this individual: tag all
Dryopidae? - Postelichus Dryopidae? - Postelichus Dryopidae? - Postelichus Dryopidae? - Postelichus Dryopidae? - Postelichus

Wonderful images!
Hope I get one of these (family) someday. Thanks for sharing!

I have my fingers crossed for you, Tim!
I'm glad you enjoyed seeing these images. If it were not for my frequent efforts to rescue the hapless victims of my landlord's pool, I doubt I would have ever encountered this beetle. I rarely go down to the creek itself (which must be their typical habitat) because it is rather densely overgrown with poison oak on both sides. :-)

My thanks... =v= and Tim for your assistance! Not disappointed at all that genus is as far as this one can go. It truly was a magnificent beetle to view in person -- shone like greenish-gold when the light hit it right!

Given comments I've read on other dryopid posts, I am going to assume that these guys must make their home in the seasonal creek that runs through the oak woodland area of the property. Last year, the creek was dry for most of the year due to drought... perhaps that's what prompted this beetle's foolhardy investigation of the pool as possible habitat.

You are right
they inhabit streams and other lotic situations; I've collected them from under partly submerged rocks and debris at the margins of creeks. They sometimes get very abundant at certain times of the year.

Thanks for the tip!
I feel a bit lame for not ever having explored the aquatic arthropod community in the creek. (See my lame excuse for this in my previous comment to Tim M.) Perhaps this year I will try harder to find some more easily accessible spots along the creek, as we have had a fair bit of rain recently and I bet things will be pretty interesting and active down there by Spring-time. :-)


Nice series
Probably keyable..will look at this later...

Postelichus sp.
Unfortunately dissection is needed to get to species (at least 3 in your area).

Dryopid, yes -- wonderful indeed; nicely shot, too!
dorsal forthcoming?

Dorsal and more...
Geez! I uploaded as quickly as I could, =v=. (*smile*)

Glad to get family confirmation. Thanks! It would be great if this one could go to genus and I do have other images if necessary, but would need info on what specific anatomy is crucial.

Tim is correct, this little beetle is indeed in the relatively new genus Postelichus Nelson, which can be distinguished Helichus Erichson by the even pubescence of the apical abdominal ventrite. And again, Tim is correct in that the specimen needs to be dissected for an ID to species. A few photos of the aedeagus would be extremely helpful, so here's to hoping that it's a male!

That is a beautiful tomentum, by the way!

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