Water Scavenger Beetle - Tropisternus

Moved

… tom murray, 9 April, 2008 - 5:43pm

Thanks again Tim

It's always nice to get the beetles to species. I just wish I'd gotten all the water off the spike.

… tom murray, 7 April, 2008 - 11:00pm

hairy legs Tropisternus

the size, less than 16mm, and the spine make this one easily Tropisternus. And from there it appears to key and match T. natator d'Orchymont. Several characteristics to note: the pubescent area on the hind femora reaches to the apex of the trochanter and just slightly beyond (some sp have more, some less); the mesosternal part of the spine/keel is wide, not narrow; and (for me the neatest one) the apical abdominal sterna with distinct median apical spine.

Looks like we already have one in BugGuide. And that one shows the depressed mesosternal keel area. But yours is a better overall ventral view, including the coloration of the legs and palpi.

… Tim Moyer, 7 April, 2008 - 10:06pm

Not T. natator

Tropisternus yes, but not T. natator. The femoral pubescence is much more reduced in that species, and it is usually more uniformly black. This is either T. mixtus or T. blatchleyi, but the difference is subtle and not seen from these photos. The all-black Tropisternus are difficult to ID without comparative material.

… Andrew Short, 8 April, 2008 - 1:14pm

Andrew

What would need to be shown to differentiate this from the 2 choices. I might be able to a detailed photo if I know what to photograph.
Thanks for help.

… tom murray, 9 April, 2008 - 5:47pm

Elytral punctation

The primary difference is that T. mixtus has elytral ground punctation of mixed size (hence the name mixtus...). This feature is present on the posterior half only, usually. Also, when I say "mixed" sizes, I don't mean huge and tiny, but rather "non-uniform". This is not an easy character to tell, even for the specialist under the microscope and usually most obvious when compared to the other option, T. blatchleyi. If you are able to capture this in a photo, great, but honestly this is a genus which I would strongly discourage species ID's from photos (except T. lateralis & T. collaris).

… Andrew Short, 14 April, 2008 - 12:33am

Genus level

Andrew, that sounds like they're difficult to distinguish, so I'll be happy with the genus for this one. Thanks.

… tom murray, 14 April, 2008 - 6:51am

thanks for the correction,

I have very little comparative material, so I'm sure I'll get a few more of these wrong. But thanks for setting this one straight.

… Tim Moyer, 8 April, 2008 - 7:40pm