Special equipment: small half-circle chocolate molds
For the filling: Place the tapioca in a pot of water and bring to a boil; cook at a boil until clear, then drain the tapioca. Add the coconut puree to desired consistency.
For the shell: Melt the chocolate and pour it into the chocolate molds, and then knock them carefully on a hard surface to release any air bubbles. Pour the excess chocolate back into the bowl of warmed chocolate. Scrape the flat portion of the mold to clean off the molds. Cool the shells to harden completely.
Pour the tapioca into the chocolate molds. Pour more chocolate over the filling, and scrape the excess again, then place the molds in the refrigerator to cool and set up completely.
To make the chocolate legs, drizzle some melted chocolate on wax paper in long strands, then freeze. Break the chocolate strands into pieces and stick them on the sides of the spiders using some melted chocolate as the glue.