Wandering Monsters: Creepy Crawlies

With the exception of the rust monster and a few touches here and there, I think that everything here is mostly fine. Of course, when it comes to monstrous bugs and bug-ike things, there is not much that could go wrong, which is why I would like to see more, I dunno, controversial stuff like angels and such.

Ankheg
Though each edition has added its personal touch to these Large, acid-spraying, insect-like monsters, they have not changed much. Though I do not find anything particularly wrong with them, I think it would be interesting to add optional powers to make them unpredictably terrifying, such as blinding acid or an agony-inducing sting.What about ankhegs that form colonies, like cow-sized termites? Why not add a touch of Alien by having them lay eggs inside creatures?

Carrion Crawler
Like the ankheg, the carrion crawler has not changed much over the editions, and like the ankheg all I can really recommend is creating some variant powers that either change what its paralyzing touch does, or just make it worse, such as by causing some kind of rotting disease, or eggs that animate corpses as zombies so that they can potentially provide a larger meal for the larva.

Purple Worm
Though it was Gargantuan in 2nd and 3rd Edition (despite my Huge-sized minis saying otherwise), I think making the baseline purple worm that big is a bit much (though at that size it does make a good candidate for an ancient, probably unique beast). At the least I would give us stats for smaller, younger versions to throw at the characters so that there is a wider level spread. Oh, also a version with serpent-like tentacles in its mouth.

Rust Monsters
A controversial change in 4th Edition—that I preferred—was how a rust monster's touch did not instantly destroy metallic gear, but instead weakened it until the encounter ended. This meant that the only way for it to completely destroy metal gear was with its encounter-based devour metal power (which recharged on a miss, so odds were pretty good it was going to eat something).

I think a good middle ground is to have a rust monster's touch impose penalties—attack and damage for weapons, Armor Class for armor and shields, and maybe reduce bonuses provided by equipment for the rest—but have them persist until the item is repaired, instead of just going away after the encounter ends. Once enough penalties have accrued (like, say, -5 or something) then the item becomes useless.

This would mean that characters still need to be careful, without completely hosing a warrior type because of a few bad rolls.

Stirge

Given that these guys still deal hit point damage with their blood drain instead of Constitution points, I think they are pretty much fine (especially because in 3rd Edition they could drian so, so much).