Spider Climb. The insect can climb difficult surfaces, including along ceilings, without needing to make an ability check.
Multiattack. The insect makes a number of attacks equal to half this spell's level (round down).
Poison Jab. Melee Attack Roll: Bonus equals your spell attack modifier, reach 10 ft. Hit: 1d6 + 3 plus the spell's level Piercing damage plus 1d4 Poison damage.
Web Bolt (Spider Only). Ranged Attack Roll: Bonus equals your spell attack modifier, range 60 ft. Hit: 1d10 + 3 plus the spell's level Bludgeoning damage, and the target's Speed is reduced to 0 until the start of the insect's next turn.
Venomous Spew (Centipede Only). Constitution Saving Throw: Your spell save DC, one creature the insect can see within 10 feet. Failure: The target has the Poisoned condition until the start of the insect's next turn.