Set aside 4 pretzels on a lined baking sheet or silicone mat, on top of a baking sheet with a bit of space between them.

Break the 'loops' off the other pretzels so that you end up with 6 roughly even 'legs' for each of the four spiders.

Melt the dark chocolate (either in a bowl over a bowl/small pot of boiling water or in the microwave in 30 second bursts, stirring in between, until melted).

With a small spoon carefully fill the gaps in the 4 pretzels you set aside. Put a little extra chocolate on top and stick a rolo onto each one (I found it needed to be upside down/narrow end down to allow for legs).

Press the ends of the pretzel 'legs' into the chocolate you have used to fill the gaps so they sit roughly evenly (see photos). Drizzle over a little extra chocolate to help the rolo and legs stay in place. Refrigerate until the chocolate hardens, a few minutes.

Melt the white chocolate and use the end of a cocktail stick or a prong from a fork to dab two eyes on each spider. Chill again to harden.