Tiger beetles are tricky, so no, I'm not sure of anything. But here goes...

All tiger beetles descended from a common ancestor, and the basic set of tiger beetle markings is a backward C on the shoulder, a long disjointed mark at the middle, and another mark that hugs the tip of each elytra.

So basically a lot of tiger beetles have the backward C. On Cicindela duodecimguttata, the backward C often has broken up until it has become two separate spots. This doesn't always happen, though. Some individuals of C. duodecimguttata have the three basic marks pretty well intact.

I think what makes this C. duodecimguttata and not C. repanda is that the backward C is well-separted from the middle mark. On repanda the backward C would touch, or nearly touch, the middle mark.

As for tiger beetle species that have lots of spots, or no spots, well, they have just evolved their markings farther away from the ancestor species.

Anyhow this is my take on it; would be glad to talk about this some more. In a few moments I want to post a C. rufiventris that doesn't look much like rufiventris!

--Stephen

Stephen Cresswell
Buckhannon, WV
www.stephencresswell.com

Thanks for the explanation, Stephen. I didn't know about the "well-separated versus nearly touching" field mark, which can be seen even from directly above, as shown on the page that Joel referred to here. I'll have to check all supposed "repanda" individuals to see whether they might actually be C. duodecimiguttata.

Interesting, I didn't know duodecimguttata could have such extensive marks. There's a specimen at the Tiger Beetles of ND that looks very similar to this, and has a description of the differences from repanda.