Climbing Cattail

This is a play on the Insectile called "Crawling Olives," which is also a caterpillar. This one's design is based on the Wooly Bear Caterpillar, while the variant design is based on the Tussock Moth Caterpillar.

This Insectile takes the shape of an S-Tetrimino, but if there is already an Insectile like that, it can be altered. If this were to have any special ability, perhaps it can change shape?

Spiked Jack

Spiders count, right? This Insectile's name comes from Jack o' Lanterns, as well as jacks the toy. Its design is based on the Horned Orb Weaver Spider. The variant design is a watermelon slice because the real Horned Orb Weaver kinda has a pattern similar to watermelon seeds.

This Insectile takes the shape of a V, like crafting a bowl in Minecraft. I liked the thought of shapes connected by the diagonal, if they're allowed. If this were to have any special ability, perhaps it can stick enemy Insectiles with webs, which they have to break out of before they can attack.

Chopping Stalk

This Insectile is a simple Praying Mantis, while its variant design in based on the Orchid Mantis. The name is based on a flower stalk, because "celery" felt like too many syllables.

This Insectile's shape is like a diagonal or zig-zagging line. I'd think this would have no special ability, but if were to, perhaps something to do with heightened damage?

Frog??

One last idea is some creature that's extremely rare to find, but covers the entire board. A frog was my first thought, considering they eat insects, and are much bigger than them. This is just a funny concept.