Hello, May We Have Some Bug SM Headcanons?
For sure! Right now, we've only gotten glimpses of him in images and no actual encounters/cutscenes, so this is really all conjuncture and vibes.
He loves the thrill of the chase. It's like a game to him, one of the few left to him with his altered body and magic! Normally this would not end well for his prey...he's almost like a cat, with how he treats them. But if he catches you, he just gives you a little nuzzle, scruffing you and carrying you back to his nest (or tower).
Very physically affectionate. Usually this entails him nuzzling you, but he also gives you light headbutts, and will use you almost as a plush toy at times...tucking you between his chest and forelimbs as he rests.
Growls and snarls at most everyone else. You are unique and fortunate in that you hear other, more positive sounds from him: clicking, chirping, even purring when he's very happy (usually when he's holding you). Plus plenty of laughter (with kind of a clicking undertone).
Based on what we've seen of the other corrupted Beasts, he's probably not able to talk...or at least doesn't talk much. He's still quite vocal in the range and amounts of sounds he makes, though. If he can talk, he has a variety of pet names for you, just like any Shadow Milk. Things like "little bug", "dewdrop", "little spark", "firefly"...