Bob Fenner has this to say about them.
"Comical in shape and behavior, for the most part unassuming, the Caribbean Arrow Crab, Stenorhynchus seticornis can be an asset in its predatory consumption of flatworms and Polychaetes (e.g. Bristleworms). Like almost all crabs, this decapod is an opportunistic omnivore, that though it's apparently small, appears passive, can and will sample other invertebrates, even fishes if it can grab them."