Potion of bug repellent; is poisonous or otherwise harmful to drink, but if you smash it over yourself, all insects (classes a, s, and x) will flee from you.

Implement hoard scarabs from D&D. They are a x, which can hide under object piles containing at least 25 gold pieces (and only object piles like that; they can’t hide under single non-gold objects or furniture or anything; possibly they can only hide under a gold-containing pile when the gold is on the top). They have a nasty poisonous bite.

When the game wants to generate one in a random location, it either creates a gold pile for the scarab to hide under where it generates or alternatively it searches around the level for a suitable gold pile and puts the scarab there. (If it can’t find one, it may just fail to generate).

They may also pop out at you from inside randomly generated gold-containing chests, possibly as a container trap effect.

Stomping boots. While wearing these, you may instakill and move into the square of all small monsters in the a, s, and x classes.

Checkerbug: like a grid bug, but can only move diagonally.

New monster “master grid bug”. When they zap you, you get a status effect that forces you to move only orthogonally like a grid bug for some time.