Quoted By:
I figure Lickitung basically eats anything it can fit into it's mouth. It reads as an aggressive, hoggish, omnivore that consumes anything within reach even vaguely edible: nuts, fruit, mushrooms, edible herbs and grasses. Pokemon wise I expect the only limitation it has to prey is whether or not they can fight back and/or if they can fit in their mouth.
Lickitung probably eat mostly small bug, grass, flying, and normal Pokemon like: Oddish, Rattata, Hoppip, Pidgey, Sparrow, Caterpie, etc.. Lickitung also have the abilities Own Tempo and Oblivious which gives them resistance/immunity to Confusion and Attraction to other Pokemon, this could imply they get attacked a lot by Pokemon with Psychic or alluring powers?