You can target 1 "Petit Moth" you control; equip this card from your hand to that target. While equipped by this effect, the original ATK/DEF of that "Petit Moth" becomes the ATK/DEF of "Cocoon of Evolution".
Rulings
Individual Card FAQs
If "Cocoon of Evolution" is Summoned or Set it is treated as a monster, if played as an Equip Spell Card it is treated as an Equip Spell Card as long as it remains on the field and could be destroyed with "Mystical Space Typhoon". Once on the field it cannot be switched from monster to Spell Card or vice versa. "Cocoon of Evolution" is NOT a Union Monster.
Netrep Rulings
The action of Equipping “Cocoon of Evolution” to a face up “Petit Moth” uses that player's Normal Summon or Set for the Turn.
When Equipped to “Petit Moth,” “Cocoon of Evolution” is an Equip Spell Card.
If “Cocoon of Evolution” is negated by “Imperial Order” while equipped to “Petit Moth,” the ATK/DEF of “Petit Moth” are not changed by the effect of “Cocoon of Evolution.”