I actually drew up a spreadsheet to estimate this: https://docs.google.com/spreadsheets/d/1xnfsDuC0ddUxvKekGLJ5QA5nrXxzked7K-k6jqUm538/edit?usp=sharing
I agree with you about the numbers: If there were say 10^15 insects then their moral weight might be in question. However there are actually more like 10^18, which is huge even for very small per-insect weightings.
I actually drew up a spreadsheet to estimate this: https://docs.google.com/spreadsheets/d/1xnfsDuC0ddUxvKekGLJ5QA5nrXxzked7K-k6jqUm538/edit?usp=sharing
I agree with you about the numbers: If there were say 10^15 insects then their moral weight might be in question. However there are actually more like 10^18, which is huge even for very small per-insect weightings.