From studying Tony's Coenobita website, I've been questioning cav IDs.
Here's his page on violascens:
http://www.tonycoenobita.com/species_violascens_ch2.htm
Note that these are all large crabs, so their structure and colors are more mature than smaller ones. The red antennae are very apparent, and the back left leg has the "cav"/indo structure. The eyes are dark and mysterious. While the main body is deep purple/blue in color, the lower extremities still show orange gradient, and the claw shows the same stripe.
In fact, running the site through babelfish translate shows the following text: "The deep purple land hermit crabyoung bodybody color mostly will be an orange yellow,but along with the growth,on the body the color then can gradually substitute by the dark blue,only remains in the chestfoot or the chelafoot terminal as soon as wipes orange yellow, but the adult body color end will transfer dark blue orthe purpleblack"
And there's pictures at the bottom showing our traditional orange/yellow "cavs".
Now, the cavipes page shows quite a different picture:
http://www.tonycoenobita.com/species_cavipes_ch2.htm
These still have the bp stripe, and the leg has the twist, but with a more exaggerated feature. However, the antennae are clearly more like Indo antennae, with large orange bases, but the feelers are not red.
I've seen pictures of some people having these more dark-brown tinted Indos (rather than the more traditional purple), and it seems that those indos might actually be real cavipes. Though the eyes are definitely dark and square like the caves we know.
In fact, the babelfish translate shows this sentence: "Can mistake in foreign very many peoplethe deep purple landhermit crab for the concave full land hermit crab,but actually so long as has a look its first antenna whether assumes red then may know,the concave full land hermit crab first antenna is not assumes red"
He is clearly addressing here the fact that foreign people (namely us) have been mistaking the violascens for the cavipes, and reiterates that if the antenna is red, then it's a violascens, not a cavipes.
I'll also point out these pictures from Japan in hermitcrabparadise that show a violascens sealed in its shell that definitely looks like our cavs:
http://www.hermitcrabparadise.com/photo ... m=26&pos=3
Every once in a while, I gotta rock the boat
Just something that popped in my head. 
