Probably a current proverb quoted by Jesus like our people in glass houses throwing stones . The yelping dogs would jump at it. Dogs are kin to wolves and infest the streets of oriental cities. Pearls look a bit like peas or acorns and would deceive the hogs until they discovered the deception. The wild boars haunt the Jordan Valley still and are not far removed from bears as they trample with their feet and rend with their tusks those who have angered them.
Some stones look like loaves of bread .
Fish , common article of food , and water -snakes could easily be substituted. Anacoluthon in this sentence in the Greek . It was used by Hillel, Philo, Isocrates, Confucius. Jesus puts it in positive form. There were false prophets in the time of the Old Testament prophets .