I'm posting this question for my grandparents who are growing a 'Bunching Onion' type from Georgia, sold in the big stores down in Florida. Their bunching onions have grown well, and have even grown a bulb in the soil. Lately they have been finding a worm that burrows in the onion bulb that creates a black tract in the bulb where it has eaten.

It does not curl up so it's not the black cutworm. I thought it was possibly an Onion Maggot, but the description they gave me differs:

Light brown, ~1" long, HARD TO SQUISH! You can't squish it with your fingers or by placing it on concrete and stepping on it.

Any ideas?