American River water beetle - Liodessus obscurellus

Moved

… Jim McClarin, 15 February, 2009 - 12:32am

Liodessus I think...

The elytra colouration does not match Neoclypeodytes..see voucher specimens from MCZ (here and here) to get an idea of what the patterning should look like. The 2 species above are synonymous with Neoclypeodytes (so ignore Bidessus). If this is indeed a Liodessus, it's L. obscurellus, a widespread, highly variable western species and one of the 2 found in CA (the other L. saratogae is an oddity found only in the Death Valley).

… Tim Loh, 15 February, 2009 - 12:13am

Well,

You're the dytiscid expert here so I'll go with your suspicions. Thanks much, Tim.

… Jim McClarin, 15 February, 2009 - 12:31am

Moved

Moved from Predacious Diving Beetles.

… Jim McClarin, 15 February, 2008 - 10:09pm

you sure it's not, say, a Liodessus?

… v belov, 19 September, 2008 - 4:25pm

Not at all.

When it comes to water beetles, ignorance is my forte ;-) Tim has been very diligent with the keys but he is a relative novice. What features would separate the two?

… Jim McClarin, 19 September, 2008 - 5:28pm

accg.to 'AmerBeetles',

besides imperceptible [on these photos] traits of clypeal margin, in Neo~ 'elytron of most speciMENs brightly patterned with a basically transverse pattern of pale spots or dark irregular fascia,' which is not the case here; and Lio~ spp are widespread and fairly common, too. Besides, for what it's worth, Neo~ 'is distinctive when only males are examined but it may be closely related to Liodessus if these 2ndary sexual features are ignored'. (Sort of a disclaimer, i guess: 'they' seem to have a pretty vague idea of how the heck, if at all, these two actually differ :)
May i now stop retyping the revered treatise? (and, btw, it's NeoclypedYtes)

… v belov, 19 September, 2008 - 6:39pm

Got it.

Fixed it.

I need a setup like Tim's I think. He's getting some very good detail in his images of pretty small beetles.

… Jim McClarin, 19 September, 2008 - 9:10pm

@#&@ man -- i missed another typo, sorry:

Neoclypeodytes...
Rule #1: shot them in dry condition, the water film distorts/conceals every important detail; and get a REAL good ventral view, too
(what an ordeal, i'll tell you, trying to make sense of this group based on photos... but i'm learning)

… v belov, 19 September, 2008 - 9:14pm

You point to 'em

I'll fix 'em :-)

… Jim McClarin, 19 September, 2008 - 9:27pm

size?

Jim, can I humbly ask to confirm the size on this as 4.5mm, or half that at about 2.25mm? At one time I thought I remembered you using a rule with 0.5mm marks?
If I'm reading the keys correctly, this beetle would seem to be from the Bidessini tribe's genera, due largely to transverse line behind the eyes, and the pronotum and elytra with sublateral plica on each side which contact the basal margins. But according to Larson, that tribe tops out at around 2.5mm. Neoclype*odytes would then be the likly genus, with several noted from CA.

… Tim Moyer, 15 February, 2008 - 9:12pm

Tim!

You amaze me! Absolutely a great catch. I just fished out its tiny cadaver and let me say that is one smaaaaall water beetle, about 2.25mm as you suggest. Thank you so much for asking, not to mention keying it out. I'll move it directly to Neoclypedotes.

… Jim McClarin, 15 February, 2008 - 10:07pm