The smashers use their raptorial arms not just to kill prey, but also to break it apart to eat. The species in the photo eats things like small crabs, and gastropod snails that live in shells. When the mantis shrimp sees one of those and goes after it, first he punches it silly, then he uses his raptorial arms to crack open the shell so that he can pick out the meat with his little forward legs, which are also specialized for that purpose.Here is a video I came across on YouTube that shows a Mantis Shrimp in an aquarium doing exactly what I described. Although the Mantis Shrimp in the video is a different species from the one in my photos, it also is a smasher. Have a look (but don't blame me for the choice of background music):
(If the video does not play or display properly above, click here to view it on YouTube.)
Tip of the hat to YouTube user accubyrd, on whose page there are a few more Mantis Shrimp videos.