In Game for my lead in Wi-fi battles.
Galvantula learns sticky web at level 65 in X and Y. If your Galvantula is higher than level 65 I suggest taking it to the Move Relearner who is located in Dendemille Town who will reteach you Galvantula sticky web in place of a heart scale.
Galvantula learns Sticky Web when leveled up to level 65. Source