You don't float living, frantic, poison-spike-covered little rabbit monsters in pitcher plants. A fly that's all weighted down in plant juice, sure, but I have a hard time seeing a victreebell never getting pricked by it spiny prey it swallows whole.
Presumably it has tough insides to keep its own acid from eating at itself, so I would assume that it's tough enough that the Victreebel doesn't care about small pokes, especially from another poison type.
OMG aren't the plants great?? I thought about a possible re-draw of Victreebel to make it more ... Real? But I'm not sure. I am currently working on Amoongus and would like to add a few details to some of the other Pokemon including a second Donphan page. We'll see.
Totally love the Weepinbell line. As in, next choice of plant Pokémon when I'm not using Chikorita as a starter in G/S/C and HG/SS. Hoppip line is awesome, too, but takes ages to train properly. Say, could you make an entry about the Hoppip line?