caterpillAr or caterpillEr ?? - lets go 50:50

Oh you wont believe what my mums done .... well she was preparing for a lesson, based on the hungry caterpillar story.  I suggested we could make cards of true and false statements for the students, so mum set off doing that.  By the end of the fourth card she re-read the statements and realised she spelt caterpillar wrong.  Every card started with "The Hungry Caterpiller ate ..." and she really meant caterpillAr - duh!!