I've heard it said you can only talk about the unknown in terms of what is known. That's probably why he used depictions of crucifixion in his expressions of hellish torture. People in life knew it was bad so it must have been terrifying to imagine an eternity of the same torture.

It's definitely an interesting piece. Bosch certainly had an fascinating way of taking common themes and twisting them into weird depictions of damnation... I never would have imagined the Prince of Hell as an insect, myself.