Occasionally, while examining a high-resolution picture on my computer monitor, I may see details in the picture that I didn’t notice while taking the picture. An example was discussed in this post. This happened again recently. When I was in Florida near the end of March, I photographed a crawling Truncatella in its habitat within a pile of seaweed stranded behind a beach. Later at home, I was disappointed that the picture of the crawling Truncatella itself wasn’t very revealing, but in the same frame I saw something else that was more interesting and that had escaped my attention in the field: a peeled empty Truncatella shell (near the right hand corner).
If I had noticed that shell in the field I would have taken it. But a day later, there was no hope of finding a particular shell that was only a few millimeters long among seaweeds even if I had remembered the exact spot where I had taken the picture. Luckily, however, I have a few similarly peeled Truncatella shells in my collection. Here is one of Truncatella caribaeensis (shell length=~4 mm).
Crabs are known to peel the shells of marine gastropods that they prey on. Could it be that tiny juvenile crabs practice their skills on the equally tiny Truncatella before moving on to larger snails? Carabid beetles, which are known predators of land snails, are another possibility. So when I found this beetle (~11 mm long) on the same beach under a pile of seaweed where there were also lots of Truncatella, I got excited. I thought maybe this was the Truncatella predator. I must admit, though, that I don’t know if this was a carabid* or not.
I took the beetle and some live Truncatella home, put them in a petri dish with some damp sand and seaweed. For about a day and a half I checked the dish several times in hopes of finding peeled shells. But, alas, there were none. The Truncatella kept crawling around while the beetle hid under the sand. Eventually, I returned them all to the beach.
The mystery peeler of Truncatella remains at large.
*Note added later: Since I posted the picture of the beach beetle on BugGuide.net, it has been identified as a Scarites sp. in the family Carabidae as I had suspected.