Avis was paranoid, not about spiders, oh no! Not about centipedes, oh no! Not about bugs, or birds, or even terrestrial pulmonate gastropod molluscs, oh no!
Avis was paranoid about tadpoles. If those little slimy eyeballs with a tail could grow legs, what else could they do? Grow claws? Tentacles? Great gnashing teeth?
And the fact that they grew into land-hopping creatures, would they jump out of their pond and leap into her bedroom at night? Avis shut her bedroom window and drew the curtains.
And then the inevitable happened, for this is a story is it not? Avis overcame her paranoia when she kissed a frog and turned into a reptile herself. They married and lived happily ever after.
She and her husband produced a bunch of sprogs, and the sprogs lived happily ever after too. One of them was able to transmogrify into a terrestrial pulmonate gastropod mollusc when it was called for, although eventually it was devoured by a hungry sibling.