Commentary for Avodah Zarah 74:13

In this section two amoraim argue over what type of locust the tannaim in the Mishnah were arguing about—a shoshiba or a susbil.
must admit, I’m not an expert on which locusts are edible. Ashkenazim stopped eating them many, many centuries ago. Ostensibly this was because they did not know which were kosher and which were not, but in reality we know why they stopped eating them. No one in Europe ate them. But people in the Middle East did eat them, and Yemenites still eat them. Some of my Ashkenazi friends have tried them. Evidently if you fry them and salt them they taste like meaty potato chips. Sounds good.

R. Yohanan says that indeed the halakhah is that doubtful cases of impurity are considered pure if they occur in the public domain. But no one told other people this until R. Yose b. Yoezer came along and taught it in public.