Human-edible winter squash are all safe for crabs. The peel, the blossoms, and the seeds are also edible. Next autumn, I hope to conduct trials on leaves of several squash plants. Winter squash is a very good source of vitamin A (butternut having the most, followed closely by pumpkin). Hubbard has 5 times the omega fatty acids that the others do.
CAUTION: Seasonal gourds sold for decorative purposes may be poisonous and should be avoided even though they may be sold alongside edible varieties in the grocery store.