there are no flies on someone

• 很机灵；不会上当

there are no flies on someone的用法和样例：

例句

1. But while China's cybercitizens may be weak, they are also ingenious.
   但是虽然中国的网民也许弱小，但他们也很机灵。
2. He had a fine head on and wanted more than anything to be cold sober and alert.
   他的头脑很机灵，应该是十分的清醒和敏捷。