Why might we say that Socrates' references to the Sophists as good candidates for teachers of virtue are not entirely serious?

Socrates needs to set up the Sophists as potential teachers of knowledge, primarily because it is essential to his argument that we admit that they fail in this purpose. Socrates is pushing his own, new kind of knowledge, which emphasizes lasting definitions of concepts rather than the wordplay and rhetoric for which the Sophists have become known. Meno and Anytus help him in this task--Meno is a follower of the Sophist teacher Gorgias, and so when Meno fails to define virtue, the failure extends by implication to Sophists generally. Anytus hates the Sophists for the reason (popular at that time) that they seem to distract their followers from worldly affairs. Socrates would wholeheartedly agree, except that he also wants to emphasize knowledge over worldly practice. Thus, in suggesting the Sophists to Anytus, Socrates is seeking to discredit both the Sophists' and Anytus' own philosophies of virtue (namely, that virtue is passed on from gentleman to gentleman). Thus, we can never take Socrates' apparently naive references to the Sophists at face value here.

What metaphor does Socrates use in reply to Meno's first attempt to define virtue? What error does this metaphor point out?

Socrates compares Meno's initial definition of virtue to a swarm of bees, since Meno has offered not a single definition of virtue but rather a "swarm" of individual virtues. Socrates then deftly uses this comparison to show Meno what he is after--this swarm of bees, he suggests, might differ slightly in shape or size, but surely there is something that makes them all "bees." Similarly, Socrates is after what makes all individual, different virtues, "virtues."

What lesson does Socrates draw from past examples of famous fathers and sons?

Socrates brings up famous pairs of fathers and sons in order to convince Anytus (who, as an Athenian conservative, thinks largely in terms of aristocratic tradition) that virtue is never taught (and so probably cannot be taught). Each of the famously virtuous fathers Socrates brings up raised a son or sons who turned out badly. Surely, Socrates argues, if virtue could be taught it would have been taught by these best of men to their beloved sons. But apparently it wasn't, so we may assume that virtue cannot be taught.