Ben, VFT's do not dissolve the hard exoskeleton of the insect. Only the soft innards are digested. However, how they react to various insects depends on many things, including heat, light, humidity, general health, and just plain old this is the way it goes sometimes. I still think the traps interacted with something in the sowbugs that turn the VFT secretions into a thickened mixture, and sealed the trap. It has happened to me mostly in terrarium growing, rarely outside.