Someone on another website suggested that its just a friendly Beedrill helping out a friend, but in the future when the Kakuna evolves those two will become mates. I thought that was a pretty nice story so I'm going with that for now.
It might be that the gradient goes from dark on the top to light on the bottom. That's kind of opposite from normal so it could be throwing you off. Plus, the forest fades off and gets darker and yet its fading into a lighter section of the background, which is kind of jarring.
Either way, sharp eye; I didn't notice that at all myself but now that you mention it I can see it. (I'm always a fan of constructive criticism!)