Conjure Worm on a String

Upon making the appropriate squiggly motion, you summon a half dozen worms on strings. Their color, either assortment or one specific hue, is determined by the caster. The quality of the worms is consistent and sufficient, meaning that the worms will withstand several years of average use, but the strings will break if mis- or overused. The worms are inert unless the string is manipulated, and are not magical unto themselves. 

The worms cannot be dispelled. 

At Higher Levels: twice as many worms are summoned with a 3rd-level slot, three times as many with a 5th-level slot, and four times as many with a 7th-level slot. With a 9th-level slot, you summon a gross of worms.