Some time since the last posting was made on this topic, but I have just joined CPUK, and hope that my very limited experience may be of assistance to someone. Regarding caterpillars and VFTs: I fed a few to several of mine, and without exception the traps closed tightly, digestion seemed to start, but the leaves turned black along the outline of the beast after about 2 days. Otherwise no permanent damage. So I just leave them to catch their own flies now, which they do extremely well. Short answer to the question: no way!