I was watching this video of Lynch making quinoa with broccoli (as you do), and at a certain point he steps outside the kitchen to tell a story of a nighttime train trip through Yugoslavia when he was young. The train stops for a while and he describes a vendor selling "sugar water" and how the air was filled with all of these moths. He gets really worked up and at one point (around the 10:11 mark) blurts out, "frog moths pulling themselves out of the earth." Maybe an early inspiration for the egg creature? It's certainly a memory that has stayed with him.
I wonder if his Yugoslavian 'frog moths' were actually cicadas? I'm sure someone else on this forum mentioned that the bug part of the amphibug looked like one - and it could also explain the time taken to emerge (periodical cicadas in the US are usually 13 or 17 years - but the emergence time can be other prime numbers - like the 11 years from 1945 - 56)
The cicada nymphs which 'pull themselves from the ground' are wingless - but then the winged form splits the larval case & crawls out - see the first minute or so of this:
All I could find, with the help of a stranger, was this. Not sure if it's directly related or not.
Next page described a woman with the "flying frogs" covering her chest and hands, that the Indians began to worship.
Please be Judy, Please be Judy, Please be Judy.