Bonus Cantrip

When you take this circle at level 2, you learn the cantrip Poison Spray.

Speech of the Arthrons

At 2nd level, you gain the ability to converse with the smallest of nature's children. Arthropods can understand your speech, and you gain the ability to decipher their noises and motions. Most Arthropods lack the intelligence to convey or understand sophisticated concepts, but a friendly one could relay what it has seen or heard in the recent past.This ability doesn’t grant you friendship with the creature, though you can combine this ability with gifts to curry favor with them as you would with any non-player character.

Unlikely Evolution

Your time spent in nature, conversing with and learning from Arthropods has had a dramatic effect on your biology. With your new druidic knowledge you are able to evolve your body beyond its initial capabilities. At 6th level select two of the following traits to evolve, at 10th level select two more and at 14th select a final two evolutions;

Ant Strength

Your frame has become light allowing your muscles to be used for more than carrying yourself. You are able to carry 3x your carrying capacity.

Antennae

You have a set of feelers that allow you to sense vibrations in the air itself. You have blind sight for 30 feet. Prerequisite: 14th level.

Chameleon Carapace

You can change the color of your carapace to match the color and texture of your surroundings. As a result, you have advantage on Stealth checks. Prerequisite: Exoskeleton, Elytra or Hardened Carapace

Compound Eyes

Your eyes evolve in such a way that color and light becomes more defined. Gain proficiency with perception checks, if you already proficient with perception you gain expertise. 

Digestive Spit

As an action you may spit corrosive digestive fluids onto a target. Target a creature's armor or weapon and roll a ranged attack, as a natural weapon you are proficient in. On hit any metal or leather on their person that is hit slowly dissolves. A non-magical weapon suffers a -1 penalty to hit and non-magical armor suffers -1 penalty to AC. Prerequisite: 10th level.

Elytra

A pair of strong fore-wings with a protective shell grow from your back allowing you to take flight. Gain a fly speed of 30. Prerequisite: Cannot be paired with Hardened Carapace.

Exoskeleton

A light but strong chitinous shell protects you. With new Natural Armor your AC becomes 13 + Dexterity modifier. You gain no benefit from wearing armor, but if you are using a shield, you can apply the shield's bonus as normal.

Fossorial Limbs

Two small limbs grow from underneath your arms that facilitate digging through sand and soft dirt with ease. As an action, you can quickly pull yourself underground and gain a burrow speed of 20 feet. Prerequisite: 10th level. 

Hardened Carapace

You’ve developed an extraordinarily strong shell. As an action, much like a pill bug you may roll into a ball completely covering yourself with your shell. While rolled and stationary you cannot move, are considered prone and your AC becomes 19. Immediately after you use the Dash action on your turn and move at least 20 feet, you can roll up into a ball and make a one melee attack as a bonus action. When rolling your shell is a natural melee weapon, you deal bludgeoning damage equal to 1d6 + your strength modifier. Prerequisite: 10th level. Cannot be paired with Elytra.  

Hive Mind

As an action you can connect your mind with up to ten willing creatures within a 30 foot radius of yourself. You can communicate telepathically with these creatures as long as they remain within the radius. Prerequisite: 10th level.   

Pulvilli

Small near imperceptible pads grow on your hands and feet that produce a natural adhesive that allows you to stick to surfaces and climb much easier. Gain a climb speed of 30. 

Segmented Body

Segmentation form in your body allowing you to become more flexible. You gain proficiency with acrobatic checks, if you are already proficient then you gain expertise. 

Venomous Stinger

You grow a segmented tail with a powerful stinger on the end, if you already have a tail it becomes segmented and grows a stinger. As an attack action you may strike with your Stinger as a natural weapon that you are proficient in. Hit: 1d6 + Str mod piercing damage, and the target must make a Constitution saving throw equal to your spell save DC, taking 2d6 poison damage on a failed save, or half as much damage on a successful one. Prerequisite: 10th level.  

Halo of Flies

At 10th level, you gain the ability to channel magic into the wind. As an action, you can expend a use of your Wild Shape feature to awaken insects to come to your aide, rather than transforming into a beast form, a mass of thousands of insects swarm around you in a 10 foot radius which obscure you, providing quarter cover. Any creature that enters or starts their turn in this area takes 3d6 piercing damage as they are accosted by hundreds of sharp bites.   

This lasts 1 minute or until you use wild shape again.

Form of the Arthron

Starting at 14th level, you gain the ability to use your wild shape to transform into stronger creatures. You may become a up to a CR 5 creature that is an arthropod.